Editing Semiconductor memory (section)

{{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.