View source for Semiconductor memory

{{Use American English|date = April 2019}}
{{Short description|Data storage device}}
{{Memory types}}

'''Semiconductor memory''' is a [[digital electronics|digital electronic]] [[semiconductor device]] used for [[digital data storage]], such as [[computer memory]]. It typically refers to devices in which data is stored within [[metal–oxide–semiconductor]] (MOS) [[memory cell (computing)|memory cells]] on a [[silicon]] [[integrated circuit]] '''memory chip'''.<ref>{{cite web |title=The MOS Memory Market |url=http://smithsonianchips.si.edu/ice/cd/MEMORY97/SEC01.PDF |website=Integrated Circuit Engineering Corporation |publisher=[[Smithsonian Institution]] |year=1997 |access-date=16 October 2019}}</ref><ref>{{cite web |title=MOS Memory Market Trends |url=http://smithsonianchips.si.edu/ice/cd/STATUS98/SEC07.PDF |website=Integrated Circuit Engineering Corporation |publisher=[[Smithsonian Institution]] |year=1998 |access-date=16 October 2019}}</ref><ref>{{cite book |last1=Veendrick |first1=Harry J. M. |title=Nanometer CMOS ICs: From Basics to ASICs |date=2017 |publisher=Springer |isbn=9783319475974 |pages=314–5 |url=https://books.google.com/books?id=Lv_EDgAAQBAJ&pg=PA314}}</ref> There are numerous different types using different semiconductor technologies. The two main types of [[random-access memory]] (RAM) are [[static RAM]] (SRAM), which uses several [[transistor]]s per memory cell, and [[dynamic RAM]] (DRAM), which uses a transistor and a [[MOS capacitor]] per cell. [[Non-volatile memory]] (such as [[EPROM]], [[EEPROM]] and [[flash memory]]) uses [[floating-gate]] memory cells, which consist of a single [[Floating-gate MOSFET|floating-gate transistor]] per cell.

Most types of semiconductor memory have the property of [[random access]],<ref name=FIFO>{{cite book|last1=Lin|first1=Wen C.|title=CRC Handbook of Digital System Design, Second Edition|date=1990|publisher=CRC Press|isbn=0849342724|page=225|url=https://books.google.com/books?id=3EYgfSsNwMUC&q=fifo%20memory%20chip&pg=PA225|access-date=4 January 2016|url-status=live|archive-url=https://web.archive.org/web/20161027130129/https://books.google.es/books?id=3EYgfSsNwMUC&lpg=PA225&dq=fifo%20memory%20chip&pg=PA225|archive-date=27 October 2016}}</ref> which means that it takes the same amount of time to access any memory location, so data can be efficiently accessed in any random order.<ref name="Dawoud">{{cite book
 |last        = Dawoud
 |first       = Dawoud Shenouda
 |author2     = R. Peplow
 |title       = Digital System Design - Use of Microcontroller
 |publisher   = River Publishers
 |date        = 2010
 |pages       = 255–258
 |url         = https://books.google.com/books?id=dtvZtUfqEOMC&q=%22semiconductor+memory%22+%22random+access%22+disk&pg=PA257
 |isbn        = 978-8792329400
 |url-status     = live
 |archive-url  = https://web.archive.org/web/20140706082433/http://books.google.com/books?id=dtvZtUfqEOMC&pg=PA257&lpg=PA257&dq=%22semiconductor+memory%22+%22random+access%22+disk&source=bl&ots=owvKMZ2DDC&sig=VRoPAV6R1pTAdFLuzms-jlage-8&hl=en&sa=X&ei=FLJZUJLqGpCUigLErYD4Aw&ved=0CFkQ6AEwBw#v=onepage&q=%22semiconductor%20memory%22%20%22random%20access%22%20disk&f=false
 |archive-date = 2014-07-06
}}</ref> This contrasts with data storage media such as [[compact disc|CDs]] which read and write data consecutively and therefore the data can only be accessed in the same sequence it was written.  Semiconductor memory also has much faster [[access time]]s than other types of data storage; a [[byte]] of data can be written to or read from semiconductor memory within a few [[nanosecond]]s, while access time for rotating storage such as hard disks is in the range of milliseconds.  For these reasons it is used for [[primary storage]], to hold the program and data the computer is currently working on, among other uses.

{{As of|2017}}, sales of semiconductor memory chips are {{US$|124 billion|long=no}} annually, accounting for {{#expr:(124/412.12)*100 round 0}}% of the [[semiconductor industry]].<ref>{{cite news |title=Annual Semiconductor Sales Increase 21.6 Percent, Top $400 Billion for First Time |url=https://www.semiconductors.org/annual-semiconductor-sales-increase-21.6-percent-top-400-billion-for-first-time/ |access-date=29 July 2019 |publisher=[[Semiconductor Industry Association]] |date=5 February 2018}}</ref> [[Shift register]]s, [[processor register]]s, [[data buffer]]s and other small digital registers that have no [[address decoder|memory address decoding mechanism]] are typically not referred to as ''memory'' although they also store digital data.

==Description==
{{See also|Computer memory}}

In a semiconductor memory chip, each [[binary digit|bit]] of binary data is stored in a tiny circuit called a ''[[Memory cell (computing)|memory cell]]'' consisting of one to several [[transistor]]s.  The memory cells are laid out in rectangular arrays on the surface of the chip.  The 1-bit memory cells are grouped in small units called ''words'' which are accessed together as a single memory address. Memory is manufactured in [[word length]] that is usually a power of two, typically ''N''=1, 2, 4 or 8 bits.

Data is accessed by means of a binary number called a [[memory address]] applied to the chip's address pins, which specifies which word in the chip is to be accessed.  If the memory address consists of ''M'' bits, the number of addresses on the chip is 2<sup>''M''</sup>, each containing an ''N'' bit word.   Consequently, the amount of data stored in each chip is ''N''2<sup>''M''</sup> bits.<ref name="Dawoud" />  The memory storage capacity for ''M'' number of [[address line]]s is given by 2<sup>''M''</sup>, which is usually in power of two: 2, 4, 8, 16, 32, 64, 128, 256 and 512  and measured in [[kilobit]]s, [[megabit]]s, [[gigabit]]s or [[terabit]]s, etc. {{as of | 2014 }} the largest semiconductor memory chips hold a few gigabits of data, but higher capacity memory is constantly being developed.    By combining several integrated circuits, memory can be arranged into a larger word length and/or address space than what is offered by each chip, often but not necessarily a [[power of two]].<ref name="Dawoud" />

The two basic operations performed by a memory chip are "''read''", in which the data contents of a memory word is read out (nondestructively), and "''write''" in which data is stored in a memory word, replacing any data that was previously stored there.  To increase data rate, in some of the latest types of memory chips such as [[DDR SDRAM]] multiple words are accessed with each read or write operation.

In addition to standalone memory chips, blocks of semiconductor memory are integral parts of many computer and data processing integrated circuits.  For example, the [[microprocessor]] chips that run computers contain [[cache memory]] to store instructions awaiting execution.

==Types==
===Volatile memory===
[[Image:RAM n.png|thumb|[[Random-access memory|RAM]] chips for computers usually come on removable [[memory module]]s like these.  Additional memory can be added to the computer by plugging in additional modules. ]]

[[Volatile memory]] loses its stored data when the power to the memory chip is turned off. However it can be faster and less expensive than non-volatile memory.  This type is used for the main memory in most computers, since data is stored on the [[hard disk]] while the computer is off.  Major types are:<ref name="Godse">{{cite book
 |last        = Godse
 |first       = A.P.
 |author2     = D.A.Godse
 |title       = Fundamentals of Computing and Programing
 |publisher   = Technical Publications
 |date        = 2008
 |location    = India
 |pages       = 1.35
 |url         = https://books.google.com/books?id=3XEIY1bjLAUC&q=%22semiconductor+memory%22+RAM+%22random+access%22+ROM+PROM&pg=SA1-PA35
 |isbn        = 978-8184315097
 |url-status     = live
 |archive-url  = https://web.archive.org/web/20140706081412/http://books.google.com/books?id=3XEIY1bjLAUC&pg=SA1-PA35&lpg=SA1-PA35&dq=%22semiconductor+memory%22+RAM+%22random+access%22+ROM+PROM&source=bl&ots=cmSseZe9-r&sig=nxViTMuUZ90bVafyjFX-izyhG1w&hl=en&sa=X&ei=7pFZUNrcAoLOiwLt2oHICg&ved=0CD0Q6AEwATgK#v=onepage&q=%22semiconductor%20memory%22%20RAM%20%22random%20access%22%20ROM%20PROM&f=false
 |archive-date = 2014-07-06
}}</ref><ref name="Arora">{{cite book
 |last        = Arora
 |first       = Ashok
 |title       = Foundations of Computer Science
 |publisher   = Laxmi Publications
 |date        = 2006
 |pages       = 39–41
 |url         = https://books.google.com/books?id=CrcoszZBMowC&q=%22semiconductor+memory%22+RAM+%22random+access%22+ROM+PROM&pg=PA39
 |isbn        = 8170089719
 |url-status     = live
 |archive-url  = https://web.archive.org/web/20140706101038/http://books.google.com/books?id=CrcoszZBMowC&pg=PA39&lpg=PA39&dq=%22semiconductor+memory%22+RAM+%22random+access%22+ROM+PROM&source=bl&ots=WkQWaH45e0&sig=tcXEKi3KMhbWj_2hXpquhk2N5Uk&hl=en&sa=X&ei=QZ9ZUIGhMsqeiAKWyIDQDQ&ved=0CGwQ6AEwCTgU#v=onepage&q=%22semiconductor%20memory%22%20RAM%20%22random%20access%22%20ROM%20PROM&f=false
 |archive-date = 2014-07-06
}}</ref>

'''RAM''' (''[[Random-access memory]]'') {{ndash}} This has become a generic term for any semiconductor memory that can be written to, as well as read from, in contrast to ROM ''(below)'', which can only be read.  All semiconductor memory, not just RAM, has the property of [[random access]].
* '''DRAM''' (''[[Dynamic random-access memory]]'') {{ndash}} This uses [[memory cell (computing)|memory cells]] consisting of one [[MOSFET]] (MOS field-effect transistor) and one [[MOS capacitor]] to store each bit. This type of RAM is the cheapest and highest in density, so it is used for the main memory in computers.  However, the [[electric charge]] that stores the data in the memory cells slowly leaks out, so the memory cells must be periodically [[memory refresh|refreshed]] (rewritten) which requires additional circuitry.  The refresh process is handled internally by the computer and is transparent to its user.
** '''FPM DRAM''' (''[[FPM DRAM|Fast page mode DRAM]]'') {{ndash}} An older type of asynchronous DRAM  that improved on previous types by allowing repeated accesses to a single "page" of memory to occur at a faster rate.  Used in the mid-1990s.
** '''EDO DRAM''' (''[[Extended data out DRAM]]'') {{ndash}} An older type of asynchronous DRAM which had faster access time than earlier types by being able to initiate a new memory access while data from the previous access was still being transferred.  Used in the later part of the 1990s.
** '''VRAM'''  (''[[Video RAM|Video random access memory]]'') {{ndash}} An older type of [[dual-ported RAM|dual-ported]] memory once used for the [[frame buffer]]s of [[video adapters]] (video cards).
** '''SDRAM''' (''[[Synchronous dynamic random-access memory]]'') {{ndash}} This added circuitry to the DRAM chip which synchronizes all operations with a clock signal added to the computer's [[memory bus]].  This allowed the chip to process multiple memory requests simultaneously using ''[[Pipeline (computing)|pipelining]]'', to increase the speed. The data on the chip is also divided into ''banks'' which can each work on a memory operation simultaneously.  This became the dominant type of computer memory by about the year 2000.
*** '''[[DDR SDRAM]]''' (''Double data rate SDRAM'') {{ndash}} This could transfer twice the data (two consecutive words) on each clock cycle by [[double pumping]] (transferring data on both the rising and falling edges of the clock pulse).  Extensions of this idea are the current (2012) technique being used to increase  memory access rate and throughput.  Since it is proving difficult to further increase the internal clock speed of memory chips, these chips increase the transfer rate by transferring more data words on each clock cycle
**** '''[[DDR2 SDRAM]]''' {{ndash}} Transfers 4 consecutive words per internal clock cycle
**** '''[[DDR3 SDRAM]]''' {{ndash}} Transfers 8 consecutive words per internal clock cycle.
**** '''[[DDR4 SDRAM]]''' {{ndash}} Transfers 16 consecutive words per internal clock cycle.
*** '''RDRAM''' (''[[Rambus DRAM]]'') {{ndash}} An alternate double data rate memory standard that was used on some Intel systems but ultimately lost out to DDR SDRAM.
**** '''[[XDR DRAM]]''' (''Extreme data rate DRAM'')
*** '''SGRAM''' (''[[Synchronous graphics RAM]]'') {{ndash}} A specialized type of SDRAM made for [[graphics adaptor]]s (video cards).  It can perform graphics-related operations such as [[bit masking]] and block write, and can open two pages of memory at once.
**** '''[[GDDR SDRAM]]''' (''Graphics DDR SDRAM'')
***** '''[[GDDR2]]'''
***** '''[[GDDR3 SDRAM]]'''
***** '''[[GDDR4 SDRAM]]'''
***** '''[[GDDR5 SDRAM]]'''
***** '''[[GDDR6 SDRAM]]'''
*** '''HBM''' (''[[High Bandwidth Memory]]'') {{ndash}} A development of SDRAM used in graphics cards that can transfer data at a faster rate.  It consists of multiple memory chips stacked on top of one another, with a wider data bus. 
** '''PSRAM''' (''[[Pseudostatic RAM]]'') {{ndash}} This is DRAM which has circuitry to perform [[memory refresh]] on the chip, so that it acts like SRAM, allowing the external memory controller to be shut down to save energy.  It is used in a few [[game console]]s such as the [[Wii]].
* '''SRAM''' (''[[Static random-access memory]]'') {{ndash}} This stores each [[bit]] of data in a circuit called a [[flip-flop (electronics)|flip-flop]], made of 4 to 6 transistors.  SRAM is less dense and more expensive per bit than DRAM, but faster and does not require [[memory refresh]].  It is used for smaller [[cache memory|cache memories]] in computers. 
* '''CAM''' (''[[Content-addressable memory]]'') {{ndash}} This is a specialized type in which, instead of accessing data using an address, a data word is applied and the memory returns the location if the word is stored in the memory.  It is mostly incorporated in other chips such as  [[microprocessor]]s where it is used for [[cache memory]].

===Non-volatile memory===
[[Non-volatile memory]] (NVM) preserves the data stored in it during periods when the power to the chip is turned off.  Therefore, it is used for the memory in portable devices, which don't have disks, and for removable [[memory cards]] among other uses. Major types are:<ref name="Godse" /><ref name="Arora" /> 

* '''ROM''' (''[[Read-only memory]]'') {{ndash}} This is designed to hold permanent data, and in normal operation is only read from, not written to.   Although many types can be written to, the writing process is slow and usually all the data in the chip must be rewritten at once.  It is usually used to store [[system software]] which must be immediately accessible to the computer, such as the [[BIOS]] program which starts the computer, and the software ([[microcode]]) for portable devices and embedded computers such as [[microcontroller]]s.
** '''MROM''' ([[Mask ROM|''Mask programmed ROM'' or ''Mask ROM'']]) {{ndash}} In this type the data is programmed into the chip when the chip is manufactured, so it is only used for large production runs.  It cannot be rewritten with new data.
** '''PROM''' (''[[Programmable read-only memory]]'') {{ndash}} In this type the data is written into an existing PROM chip before it is installed in the circuit, but it can only be written once.  The data is written by plugging the chip into a device called a PROM programmer.
** '''EPROM''' (''[[Erasable programmable read-only memory]]'' or UVEPROM) {{ndash}} In this type the data in it can be rewritten by removing the chip from the circuit board, exposing it to an [[ultraviolet light]] to erase the existing data, and plugging it into a PROM programmer. The IC package has a small transparent "window" in the top to admit the UV light. It is often used for prototypes and small production run devices, where the program in it may have to be changed at the factory. [[Image:4Mbit EPROM Toshiba TC574200D (2).jpg|thumb|4M EPROM, showing transparent window used to erase the chip]]
** '''EEPROM''' (''[[Electrically erasable programmable read-only memory]]'') {{ndash}} In this type the data can be rewritten electrically, while the chip is on the circuit board, but the writing process is slow.  This type is used to hold [[firmware]], the low level microcode which runs hardware devices, such as the [[BIOS]] program in most computers, so that it can be updated.
* '''NVRAM''' (''[[Non-volatile random-access memory]]'')
** '''FRAM''' (''[[Ferroelectric RAM]]'') {{ndash}} One type of nonvolatile RAM.
* '''[[Flash memory]]''' {{ndash}} In this type the writing process is intermediate in speed between EEPROMS and RAM memory; it can be written to, but not fast enough to serve as main memory.  It is often used as a semiconductor version of a [[hard disk]], to store files.   It is used in portable devices such as PDAs, [[USB flash drives]], and removable [[memory card]]s used in [[digital camera]]s and [[cellphone]]s.

==History==
{{See also|Computer memory|Memory cell (computing)}}

Early [[computer memory]] consisted of [[magnetic-core memory]], as early [[solid-state electronic]] [[semiconductors]], including [[transistors]] such as the [[bipolar junction transistor]] (BJT), were impractical for use as digital storage elements ([[Memory cell (computing)|memory cells]]). The earliest semiconductor memory dates back to the early 1960s, with bipolar memory, which used bipolar transistors.<ref name="computerhistory1966">{{cite web |title=1966: Semiconductor RAMs Serve High-speed Storage Needs |url=https://www.computerhistory.org/siliconengine/semiconductor-rams-serve-high-speed-storage-needs/ |website=[[Computer History Museum]] |access-date=19 June 2019}}</ref> '''Bipolar semiconductor memory '''made from [[discrete device]]s was first shipped by [[Texas Instruments]] to the [[United States Air Force]] in 1961. The same year, the concept of [[Solid-state electronics|solid-state]] memory on an [[integrated circuit]] (IC) chip was proposed by [[applications engineers|applications engineer]] Bob Norman at [[Fairchild Semiconductor]].<ref name="computerhistory-timeline">{{cite web |title=Semiconductor Memory Timeline Notes |url=http://corphist.computerhistory.org/corphist/documents/doc-4803f82fa3ba8.pdf |website=[[Computer History Museum]] |date=November 8, 2006 |access-date=2 August 2019}}</ref> The '''first single-chip''' memory IC was the BJT 16-bit IBM SP95 fabricated in December 1965, engineered by Paul Castrucci.<ref name="computerhistory1966"/><ref name="computerhistory-timeline"/> While bipolar memory offered improved performance over magnetic-core memory, it could not compete with the lower price of magnetic-core memory, which remained dominant up until the late 1960s.<ref name="computerhistory1966"/> Bipolar memory failed to replace magnetic-core memory because bipolar [[Flip-flop (electronics)|flip-flop]] circuits were too large and expensive.<ref>{{cite book |last1=Orton |first1=John W. |title=Semiconductors and the Information Revolution: Magic Crystals that made IT Happen |date=2009 |publisher=[[Academic Press]] |isbn=978-0-08-096390-7 |page=104 |url=https://books.google.com/books?id=6YLL9197NfMC&pg=PA104}}</ref>

=== MOS memory ===
{{See also|MOSFET}}

The advent of the [[metal–oxide–semiconductor field-effect transistor]] (MOSFET),<ref name="sciencedirect">{{cite web |title=Transistors – an overview |url=https://www.sciencedirect.com/topics/computer-science/transistors |website=[[ScienceDirect]] |access-date=8 August 2019}}</ref> invented by [[Mohamed M. Atalla]] and [[Dawon Kahng]] at [[Bell Labs]] in 1959,<ref name="computerhistory">{{cite journal |url=https://www.computerhistory.org/siliconengine/metal-oxide-semiconductor-mos-transistor-demonstrated/ |title=1960 – Metal Oxide Semiconductor (MOS) Transistor Demonstrated |journal=The Silicon Engine |publisher=[[Computer History Museum]]}}</ref> enabled the practical use of [[metal–oxide–semiconductor]] (MOS) transistors as [[memory cell (computing)|memory cell]] storage elements, a function previously served by [[magnetic-core memory|magnetic cores]] in [[computer memory]].<ref name="sciencedirect"/> MOS memory was developed by John Schmidt at [[Fairchild Semiconductor]] in 1964.<ref name="computerhistory1970"/><ref>{{Cite book |url=https://books.google.com/books?id=kG4rAQAAIAAJ&q=John+Schmidt |title=Solid State Design. Vol. 6 |date=1965 |publisher=Horizon House}}</ref> In addition to higher performance, MOS memory was cheaper and consumed less power than magnetic-core memory.<ref name="computerhistory1970">{{cite web |title=1970: MOS Dynamic RAM Competes with Magnetic Core Memory on Price |url=https://www.computerhistory.org/siliconengine/mos-dynamic-ram-competes-with-magnetic-core-memory-on-price/ |website=[[Computer History Museum]] |access-date=29 July 2019}}</ref> This led to MOSFETs eventually replacing magnetic cores as the standard storage elements in computer memory.<ref name="sciencedirect"/>

In 1965, J. Wood and R. Ball of the [[Royal Radar Establishment]] proposed digital storage systems that use [[CMOS]] (complementary MOS) memory cells, in addition to MOSFET [[power devices]] for the [[power supply]], switched cross-coupling, [[switches]] and [[delay-line memory|delay-line storage]].<ref>{{cite conference |last1=Wood |first1=J. |last2=Ball |first2=R. |title=The use of insulated-gate field-effect transistors in digital storage systems |conference=1965 IEEE International Solid-State Circuits Conference. Digest of Technical Papers |date=February 1965 |volume=VIII |pages=82–83 |doi=10.1109/ISSCC.1965.1157606}}</ref> The development of [[silicon-gate]] [[MOS integrated circuit]] (MOS IC) technology by [[Federico Faggin]] at Fairchild in 1968 enabled the production of MOS [[memory chip]]s.<ref>{{cite web |title=1968: Silicon Gate Technology Developed for ICs |url=https://www.computerhistory.org/siliconengine/silicon-gate-technology-developed-for-ics/ |website=[[Computer History Museum]] |access-date=10 August 2019}}</ref> [[NMOS logic|NMOS]] memory was commercialized by [[IBM]] in the early 1970s.<ref>{{cite journal |last1=Critchlow |first1=D. L. |title=Recollections on MOSFET Scaling |journal=IEEE Solid-State Circuits Society Newsletter |date=2007 |volume=12 |issue=1 |pages=19–22 |doi=10.1109/N-SSC.2007.4785536 |doi-access=free }}</ref> MOS memory overtook magnetic core memory as the dominant memory technology in the early 1970s.<ref name="computerhistory1970"/>

The term "memory" when used with reference to computers most often refers to volatile [[random-access memory]] (RAM). The two main types of volatile RAM are [[static random-access memory]] (SRAM) and [[dynamic random-access memory]] (DRAM). Bipolar SRAM was invented by Robert Norman at Fairchild Semiconductor in 1963,<ref name="computerhistory1966"/> followed by the development of MOS SRAM by John Schmidt at Fairchild in 1964.<ref name="computerhistory1970"/> SRAM became an alternative to magnetic-core memory, but required six MOS transistors for each [[bit]] of data.<ref name="ibm100">{{cite web |title=DRAM |url=https://www.ibm.com/ibm/history/ibm100/us/en/icons/dram/ |website=IBM100 |publisher=[[IBM]] |access-date=20 September 2019 |date=9 August 2017}}</ref> Commercial use of SRAM began in 1965, when IBM introduced their SP95 SRAM chip for the [[IBM System/360|System/360 Model 95]].<ref name="computerhistory1966"/>

[[Toshiba]] introduced bipolar DRAM [[Memory cell (computing)|memory cells]] for its Toscal BC-1411 [[electronic calculator]] in 1965.<ref name="bc-spec">{{cite web|url=http://www.oldcalculatormuseum.com/s-toshbc1411.html|title=Spec Sheet for Toshiba "TOSCAL" BC-1411|website=Old Calculator Web Museum|access-date=8 May 2018|url-status=live|archive-url=https://web.archive.org/web/20170703071307/http://www.oldcalculatormuseum.com/s-toshbc1411.html|archive-date=3 July 2017}}</ref><ref name="bc">[http://www.oldcalculatormuseum.com/toshbc1411.html Toshiba "Toscal" BC-1411 Desktop Calculator] {{webarchive|url=https://web.archive.org/web/20070520202433/http://www.oldcalculatormuseum.com/toshbc1411.html |date=2007-05-20 }}</ref> While it offered improved performance over magnetic-core memory, bipolar DRAM could not compete with the lower price of the then dominant magnetic-core memory.<ref>{{cite web |title=1966: Semiconductor RAMs Serve High-speed Storage Needs |url=https://www.computerhistory.org/siliconengine/semiconductor-rams-serve-high-speed-storage-needs/ |website=Computer History Museum}}</ref> MOS technology is the basis for modern DRAM. In 1966, Dr. [[Robert H. Dennard]] at the [[IBM Thomas J. Watson Research Center]] was working on MOS memory. While examining the characteristics of MOS technology, he found it was capable of building [[capacitors]], and that storing a charge or no charge on the MOS capacitor could represent the 1 and 0 of a bit, while the MOS transistor could control writing the charge to the capacitor. This led to his development of a single-transistor DRAM memory cell.<ref name="ibm100"/> In 1967, Dennard filed a patent under IBM for a single-transistor DRAM memory cell, based on MOS technology.<ref>{{cite web |title=Robert Dennard |url=https://www.britannica.com/biography/Robert-Dennard |website=[[Encyclopedia Britannica]] |access-date=8 July 2019}}</ref> This led to the first commercial DRAM IC chip, the [[Intel 1103]], in October 1970.<ref name="Intel2003">{{cite web |title=Intel: 35 Years of Innovation (1968–2003) |url=https://www.intel.com/Assets/PDF/General/35yrs.pdf |publisher=Intel |year=2003 |access-date=26 June 2019 |archive-url=https://web.archive.org/web/20211104070452/https://www.intel.com/Assets/PDF/General/35yrs.pdf |archive-date=4 November 2021 |url-status=dead}}</ref><ref name="HC">[http://history-computer.com/ModernComputer/Basis/dram.html ''The DRAM memory of Robert Dennard'']. history-computer.com.</ref><ref name="Lojek-1103">{{cite book |last1=Lojek |first1=Bo |title=History of Semiconductor Engineering |date=2007 |publisher=[[Springer Science & Business Media]] |isbn=9783540342588 |pages=362–363 |url=https://books.google.com/books?id=2cu1Oh_COv8C&pg=PA362 |quote=The i1103 was manufactured on a 6-mask silicon-gate P-MOS process with 8 μm minimum features. The resulting product had a 2,400&nbsp;µm, 2 memory cell size, a die size just under 10&nbsp;mm<sup>2</sup>, and sold for around $21.}}</ref> [[Synchronous dynamic random-access memory]] (SDRAM) later debuted with the [[Samsung Electronics|Samsung]] KM48SL2000 chip in 1992.<ref>{{cite web |title=KM48SL2000-7 Datasheet |url=https://www.datasheetarchive.com/KM48SL2000-7-datasheet.html |publisher=[[Samsung]] |access-date=19 June 2019 |date=August 1992}}</ref><ref name="electronic-design">{{cite journal |title=Electronic Design |journal=[[Electronic Design]] |date=1993 |volume=41 |issue=15–21 |url=https://books.google.com/books?id=QmpJAQAAIAAJ |publisher=Hayden Publishing Company |quote=The first commercial synchronous DRAM, the Samsung 16-Mbit KM48SL2000, employs a single-bank architecture that lets system designers easily transition from asynchronous to synchronous systems.}}</ref>

The term "memory" is also often used to refer to [[non-volatile memory]], specifically [[flash memory]]. It has origins in [[read-only memory]] (ROM). [[Programmable read-only memory]] (PROM) was invented by [[Wen Tsing Chow]] in 1956, while working for the Arma Division of the American Bosch Arma Corporation.<ref name="Huang2008">{{cite book |author=Han-Way Huang |title=Embedded System Design with C805 |url=https://books.google.com/books?id=3zRtCgAAQBAJ&pg=PA22 |date=5 December 2008 |publisher=Cengage Learning |isbn=978-1-111-81079-5 |page=22 |url-status=live |archive-url=https://web.archive.org/web/20180427092847/https://books.google.com/books?id=3zRtCgAAQBAJ&pg=PA22 |archive-date=27 April 2018}}</ref><ref name="AufaureZimányi2013">{{cite book |author1=Marie-Aude Aufaure |author2=Esteban Zimányi |title=Business Intelligence: Second European Summer School, eBISS 2012, Brussels, Belgium, July 15–21, 2012, Tutorial Lectures |url=https://books.google.com/books?id=7iK5BQAAQBAJ&pg=PA136 |date=17 January 2013 |publisher=Springer |isbn=978-3-642-36318-4 |page=136 |url-status=live |archive-url=https://web.archive.org/web/20180427092847/https://books.google.com/books?id=7iK5BQAAQBAJ&pg=PA136 |archive-date=27 April 2018}}</ref> In 1967, Dawon Kahng and [[Simon Sze]] of Bell Labs proposed that the [[Floating gate MOSFET|floating gate]] of a MOS [[semiconductor device]] could be used for the cell of a reprogrammable [[read-only memory]] (ROM), which led to [[Dov Frohman]] of [[Intel]] inventing [[EPROM]] (erasable PROM) in 1971.<ref name="computerhistory1971">{{cite web |title=1971: Reusable semiconductor ROM introduced |url=https://www.computerhistory.org/storageengine/reusable-semiconductor-rom-introduced/ |website=[[Computer History Museum]] |access-date=19 June 2019}}</ref> [[EEPROM]] (electrically erasable PROM) was developed by Yasuo Tarui, Yutaka Hayashi and Kiyoko Naga at Japan's [[Ministry of International Trade and Industry]] (MITI) [[Electrotechnical Laboratory]] in 1972.<ref>{{cite journal |last1=Tarui |first1=Y. |last2=Hayashi |first2=Y. |last3=Nagai |first3=K. |title=Electrically reprogrammable nonvolatile semiconductor memory |journal=IEEE Journal of Solid-State Circuits |date=1972 |volume=7 |issue=5 |pages=369–375 |doi=10.1109/JSSC.1972.1052895 |issn=0018-9200 |bibcode=1972IJSSC...7..369T}}</ref> Flash memory was invented by [[Fujio Masuoka]] at [[Toshiba]] in the early 1980s.<ref>{{cite web |last=Fulford |first=Benjamin |title=Unsung hero |work=Forbes |date=24 June 2002 |access-date=18 March 2008 |url=https://www.forbes.com/global/2002/0624/030.html |url-status=live |archive-url=https://web.archive.org/web/20080303205125/http://www.forbes.com/global/2002/0624/030.html |archive-date=3 March 2008 |df=dmy-all }}</ref><ref>{{patent|US|4531203|Fujio Masuoka}}.</ref> Masuoka and colleagues presented the invention of [[NOR flash]] in 1984,<ref>{{cite web |title=Toshiba: Inventor of Flash Memory |url=http://www.flash25.toshiba.com |website=[[Toshiba]] |access-date=20 June 2019}}</ref> and then [[NAND flash]] in 1987.<ref>{{cite conference |title=New ultra high density EPROM and flash EEPROM with NAND structure cell |last1=Masuoka |first1=F. |last2=Momodomi |first2=M. |last3=Iwata |first3=Y. |last4=Shirota |first4=R. |year=1987 |conference=[[International Electron Devices Meeting|IEDM]] 1987 |book-title=Electron Devices Meeting, 1987 International |publisher=[[IEEE]] |df=dmy |doi=10.1109/IEDM.1987.191485}}</ref> Toshiba commercialized NAND flash memory in 1987.<ref name=":0">{{cite web |title=1987: Toshiba Launches NAND Flash |url=https://www.eweek.com/storage/1987-toshiba-launches-nand-flash |website=[[eWeek]] |date=April 11, 2012 |access-date=20 June 2019}}</ref><ref>{{cite web |title=1971: Reusable semiconductor ROM introduced |url=https://www.computerhistory.org/storageengine/reusable-semiconductor-rom-introduced/ |website=[[Computer History Museum]] |access-date=19 June 2019}}</ref>

== Applications ==
{{See also|List of MOSFET applications}}

{| class="wikitable sortable"
|+ MOS memory applications
! style="width:20%" | MOS memory type
! {{Abbr|Abbr.|Abbreviation}}
! style="width:10%" | MOS [[Memory cell (computing)|memory cell]]
! Applications
|-
|[[Static random-access memory]]
|SRAM
|[[MOSFETs]]
|[[Cache memory]], [[cell phones]], [[eSRAM]], [[mainframes]], [[multimedia computer]]s, [[Telecommunications network|networking]], [[personal computers]], [[Server (computing)|servers]], [[supercomputers]], [[telecommunications]], [[workstations]],<ref name="Veendrick267">{{cite book |last1=Veendrick |first1=Harry |title=Deep-Submicron CMOS ICs: From Basics to ASICs |date=2000 |publisher=[[Kluwer Academic Publishers]] |isbn=9044001116 |pages=267–8 |edition=2nd |url=https://xdevs.com/doc/_Books/ASIC_Design/deep-submicron%20cmos%20ics.%20from%20basics%20to%20asics%20(veendrick-1998).pdf |access-date=2019-11-14 |archive-date=2020-12-06 |archive-url=https://web.archive.org/web/20201206130923/https://xdevs.com/doc/_Books/ASIC_Design/deep-submicron%20cmos%20ics.%20from%20basics%20to%20asics%20(veendrick-1998).pdf |url-status=dead }}</ref> [[DVD]] [[disk buffer]],<ref name="Veendrick315">{{cite book |last1=Veendrick |first1=Harry J. M. |title=Nanometer CMOS ICs: From Basics to ASICs |date=2017 |publisher=Springer |isbn=9783319475974 |page=315 |edition=2nd |url=https://books.google.com/books?id=Lv_EDgAAQBAJ&pg=PA315}}</ref>  [[data buffer]],<ref name="Veendrick264">{{cite book |last1=Veendrick |first1=Harry J. M. |title=Nanometer CMOS ICs: From Basics to ASICs |edition=2nd |date=2017 |publisher=Springer |isbn=9783319475974 |page=264 |url=https://books.google.com/books?id=Lv_EDgAAQBAJ&pg=PA264}}</ref> [[nonvolatile BIOS memory]]
|-
|[[Dynamic random-access memory]]
|DRAM
|[[MOSFET]], [[MOS capacitor]]
|[[Camcorders]], [[Embedded system|embedded logic]], [[eDRAM]], [[graphics card]], [[hard disk drive]] (HDD), networks, personal computers, [[personal digital assistants]], [[Printer (computing)|printers]],<ref name="Veendrick267"/> [[main memory|main computer memory]], [[desktop computers]], servers, [[solid-state drives]], [[video memory]],<ref name="Veendrick315"/> [[framebuffer]] memory<ref name="Shoup_SuperPaint">{{cite web |url=http://accad.osu.edu/~waynec/history/PDFs/Annals_final.pdf |archive-url=https://web.archive.org/web/20040612215245/http://accad.osu.edu/~waynec/history/PDFs/Annals_final.pdf |archive-date=2004-06-12 |title=SuperPaint: An Early Frame Buffer Graphics System |author=Richard Shoup |publisher=IEEE |work=Annals of the History of Computing |year=2001 |url-status=dead }}</ref><ref>{{cite conference |last1=Goldwasser |first1=S.M. |title=Computer Architecture For Interactive Display Of Segmented Imagery |conference=Computer Architectures for Spatially Distributed Data |date=June 1983 |publisher=[[Springer Science & Business Media]] |isbn=9783642821509 |pages=75–94 (81) |url=https://books.google.com/books?id=8MuoCAAAQBAJ&pg=PA81}}</ref>
|-
|[[Ferroelectric random-access memory]]
|FRAM
|MOSFET, Ferroelectric capacitor
|[[Non-volatile memory]], [[radio-frequency identification]] (RF identification), [[smart cards]]<ref name="Veendrick267"/><ref name="Veendrick315"/>
|-
|[[Read-only memory]]
|ROM
|MOSFET
|[[Character generator]]s, [[electronic musical instruments]], [[laser printer]] [[computer font|fonts]], [[video game]] [[ROM cartridge]]s, [[word processor]] [[dictionary]] data<ref name="Veendrick267"/><ref name="Veendrick315"/>
|-
|[[Erasable programmable read only memory|Erasable programmable read-only memory]]
|EPROM
|[[Floating-gate MOSFET]]
|[[CD-ROM drives]], [[embedded system|embedded]] memory, [[code]] [[Computer data storage|storage]], [[modems]]<ref name="Veendrick267"/><ref name="Veendrick315"/>
|-
|[[Electrically erasable programmable read-only memory]]
|EEPROM
|Floating-gate MOSFET
|[[Anti-lock braking system]]s, [[air bags]], [[car radio]]s, [[cell phones]], [[consumer electronics]], [[cordless telephones]], [[disk drives]], embedded memory, [[aircraft flight control system|flight controllers]], [[military technology]], modems, [[pagers]], printers, [[set-top box]], smart cards<ref name="Veendrick267"/><ref name="Veendrick315"/>
|-
|[[Flash memory]]
|Flash
|Floating-gate MOSFET
|[[Parallel ATA|ATA]] [[Microcontroller|controller]]s, [[battery-powered]] applications, telecommunications, code storage, [[digital cameras]], [[MP3 players]], [[portable media players]], BIOS memory,<ref name="Veendrick267"/> [[USB flash drive]],<ref>{{cite web |last1=Windbacher |first1=Thomas |title=Flash Memory |url=http://www.iue.tuwien.ac.at/phd/windbacher/node14.html |website=[[TU Wien]] |date=June 2010 |access-date=20 December 2019}}</ref> [[digital TV]], [[e-books]], [[memory cards]], [[mobile devices]], set-top box, [[smartphones]], solid-state drives, [[tablet computers]]<ref name="Veendrick315"/>
|-
|[[Non-volatile random-access memory]]
|NVRAM
|Floating-gate MOSFETs
|[[Medical equipment]], [[spacecraft]]<ref name="Veendrick267"/><ref name="Veendrick315"/>
|}

==See also==
*[[Electronics industry]]
*[[Semiconductor industry]]

==References==
{{reflist}}

{{Authority control}}

{{DEFAULTSORT:Semiconductor Memory}}
[[Category:Digital electronics]]
[[Category:Computer memory]]
[[Category:Integrated circuits]]
[[Category:MOSFETs]]