A MOSFET is a metal oxide semiconductor field-effect transistor.
MOS transistors consist of two diodes separated by a gate region. A transistor is used as a voltage-controlled current source. The metal-oxide-semiconductor field effect transistor (MOSFET) is a device made on a semiconductor substrate, typically silicon. There are two regions of semiconductor material called the source and the drain. These regions contain more electrons than does the substrate. The source and drain are connected by a slab of the substrate called the channel. An n-channel transistor uses n-type semiconductors for the channel. The channel is covered by a thin film of oxide which acts as an insulator. On top of the oxide layer is a metal electrode, called the gate. The combination of the channel, oxide layer, and gate acts as a capacitor. The substrate is silicon, the oxide layer is silicon dioxide, and the bottom electrode is aluminum.