CMOS

CMOS technology and high-density integrated circuits (VLSI)

Modern electronic circuits use the field-effect transistor (FET) and in particular the Metal-oxide-semiconductor field-effect transistor (MOSFET).

In 1930, Julius Edgar Lilienfeld (1881-1963), from the University of Leipzig applied for a patent in which he described an element bearing resemblance to the MOS transistor and which could have been the first transistor in history. We had to wait until the 1960s in order to see the arrival of such devices, whose development was made possible with the noted progress in the field of bipolar transistors and in particular in the resolution of problems with the oxide semi-conductor interface. Today, the MOS transistor is the key element of digital integrated circuits on a large scale due to both the simplicity in its production and its small size.

The MOS transistor is a FET made up of a semiconductor substrate (B or Bulk) and covered with a layer of oxide on which there is the gate electrode (G or Gate). By applying a potential difference between the gate (G) and the substrate (B), an electric field in the semi-conductor is created causing the dominant carriers to be pushed back far from the oxide semi-conductor interface, leaving the non-dominant carriers coming from two complementary sectors in the substrate known as the source (S) and the drain (D). These sectors form a thin layer of mobile charges known as a canal. These charges are able to transit between the drain and the source, both of which are found at the extreme ends of the canal.

Complementary Metal Oxide Silicon (CMOS) technology evolved from MOSFET technology and is used for Very L<\u>arge Scale Integration (VLSI) systems. Thanks to the properties of complementary MOS transistors, this silicon planar technology has enabled the creation of low-cost and low-energy circuits. These advantages have meant that this technology is recognized as the central technology behind the microelectronics industry.

The underlying idea behind CMOS technology is to create pairs of complementary transistors (i.e. a P-type coupled transistor and an N-type coupled transistor). Each pair is able to create logic gates based on Boolean principles used in digital electronics.

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