Concept

CMOS

Overview

Complementary metal–oxide–semiconductor (CMOS SEE-moss) is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSFETs for logic functions. CMOS technology is used for constructing integrated circuit (IC) chips, including microprocessors, microcontrollers, memory chips, and other digital logic circuits. CMOS overtook NMOS logic as the dominant MOSFET fabrication process for very large-scale integration (VLSI) chips in the 1980s, replacing earlier transistor–transistor logic (TTL) technology at the same time. CMOS has since remained the standard fabrication process for MOSFET semiconductor devices. As of 2011, 99% of IC chips, including most digital, analog and mixed-signal ICs, were fabricated using CMOS technology.

In 1948, John Bardeen and Walter Brattain, the original inventors of transistor technology, patented an insulated-gate transistor (IGFET) with an inversion layer. Bardeen's concept forms the basis of CMOS technology today. The CMOS process was presented by Fairchild Semiconductor's Frank Wanlass and Chih-Tang Sah at the International Solid-State Circuits Conference in 1963. Wanlass later filed US patent 3,356,858 for CMOS circuitry and it was granted in 1967. RCA commercialized the technology with the trademark "COS-MOS" in the late 1960s, forcing other manufacturers to find another name, leading to "CMOS" becoming the standard name for the technology by the early 1970s.

Two important characteristics of CMOS devices are high noise immunity and low static power consumption. Since one transistor of the MOSFET pair is always off, the series combination draws significant power only momentarily during switching between on and off states. Consequently, CMOS devices do not produce as much waste heat as other forms of logic, like NMOS logic or transistor–transistor logic (TTL), which normally have some standing current even when not changing state. These characteristics allow CMOS to integrate a high density of logic functions on a chip. It was primarily for this reason that CMOS became the most widely used technology to be implemented in VLSI chips.

The phrase "metal–oxide–semiconductor" is a reference to the physical structure of MOS field-effect transistors, having a metal gate electrode placed on top of an oxide insulator, which in turn is on top of a semiconductor material. Aluminium was once used but now the material is polysilicon. Other metal gates have made a comeback with the advent of high-κ dielectric materials in the CMOS process, as announced by IBM and Intel for the 45 nanometer node and smaller sizes.

CMOS technology is also used for analog circuits such as image sensors (CMOS sensors), data converters, RF circuits (RF CMOS), and highly integrated transceivers for many types of communication.

Overview adapted from Wikipedia (CC BY-SA 4.0; see the article history for authors).

Possible passages

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1. G. Van Santvoord, of Oriel College, Oxford, and Yale University. The Press is publisher, on both sides of the Atlantic, to the Carnegie Endowment for International Peace, many of whose books have been printed at Oxford. Special mention may be made of the first volumes, printed at the Press and recently published, of the British Section of the great _Economic and Social History of the World War_ undertaken by the…

   Oxford University Press, Some Account of the Oxford University Press, 1468-1921

   Close in meaning to CMOS; the term itself is not named.

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2. We have suffered much from critics who consider it sufficient to criticise our procedure on the slender basis of a knowledge of the dictionary meanings of such terms. For example, a one-to-one correlation depends on the notion of a class with only one member, and this notion is defined without appeal to the concept of the number one. The notion of diversity is all that is wanted. Thus the class α has only one…

   Alfred North Whitehead, The organisation of thought, educational and scientific

   States what CMOS is.

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3. "Mnemic phenomena" are defined as those due to engrams; in animals, they are specially associated with the nervous system, but not exclusively, even in man. When two stimuli occur together, one of them, occurring afterwards, may call out the reaction for the other also. We call this an "ekphoric influence," and stimuli having this character are called "ekphoric stimuli." In such a case we call the engrams of the two…

   Bertrand Russell, The Analysis of Mind

   States what CMOS is.

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Related ideas

• Simon & Schuster
• Integrated circuit
• Massachusetts Institute of Technology
• Relay
• Sheffer stroke
• Transistor
• Bit
• Johns Hopkins University Press
• MOSFET
• Transistor–transistor logic
• Prentice Hall
• Complement (set theory)
• De Morgan's laws
• Cambridge University Press
• NMOS logic
• PMOS logic
• Field-effect transistor
• Flip-flop (electronics)
• Bipolar junction transistor

Opposing perspectives

• Static random-access memory

Place in the tradition

Part of Logic gate.

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