The MOSFET was the subject of a patent in 1933, but did not reach commercial maturity until about thirty years later. The delay was principally due to a lack of understanding of the importance of the oxide/semiconductor interface, and to the time taken to develop suitable fabrication procedures, notably for the growth of the thin gate oxide. Now, in the early 21st century, the science of silicon, and the art and technology of its processing into electronic devices have reached such a state of maturity that billions of Si MOSFETs are made weekly. The claim that the Si MOSFET is the most abundant object made by mankind is difficult to refute.

In this chapter the so-called ‘long-channel’ FET is considered. The basic electrostatics of the device is developed, and the DC current-voltage characteristics are derived using two models that are very widely used in the simulation of Si MOSFET integrated circuits: PSP and SPICE. PSP stands for ‘Penn-State Philips’, after the two organizations that have been largely instrumental in bringing this surface-potential model to a state of commercial viability. It is the Compact Model Council's new, industrialstandard, MOSFET model. SPICE stands for ‘Simulation Program with Integrated Circuit Emphasis’. It was originally developed by Lawrence Nagel at the University of California at Berkeley in the mid-1970s, and has evolved extensively since then. PSP is surface-potential based, whereas SPICE is threshold-voltage based.