Metal Oxide Field Effect Transistor

The metal-oxide-semiconductor field-effect transistor (MOSFET/MOS-FET/MOS FET) is a device employed for amplifying or for switching electronic signals. The fundamental principle of the device was first planned by Julius Edgar Lilienfeld in the year 1925. In MOSFETs, a voltage on the oxide-insulated gate electrode can make a conducting channel in between the two other contacts called drain and source. The channel may be of n-type or p-type, and is so called an nMOSFET or a pMOSFET (as well commonly nMOS, pMOS). It is by far the very much common transistor in both digital and analog circuits, although the bipolar junction transistor was at one time very much common.

The 'metal' in the name is now frequently a misnomer since the previously metal gate material is currently often a layer of poly silicon (polycrystalline silicon). Aluminium had been the gate material till the mid 1970s, while poly silicon became dominant, because of its capability to make self-aligned gates. Metallic gates are regaining popularity, as it is hard to increase the speed of operation of transistors with no metal gates.

IGFET is a related word meaning insulated-gate field-effect transistor, and is approximately synonymous with MOSFET, although it can refer to FETs with a gate insulator which is not oxide. Other synonym is MISFET for metal-insulator-semiconductor FET.