MOSFET-Metal Oxide Silicon Field Effect Transistor is a device that controls a current between two contacts (Source and Drain)using a voltage contact (Gate). The device uses a surface effect to create a n-type region in a p-type substrate (or the converse).

The MOSFET transistor is ubiquitous in modern life because it is the transistor type most commonly used in integrated circuits, the basis of almost all modern computers and electronic devices. The MOSFET transistor is well-suited for this role due to its low power consumption and dissipation, low waste heat, and low mass production costs. A modern integrated circuit can contain billions of MOSFETs. MOSFET transistors are present in devices ranging from cellular phones and digital watches to enormous supercomputers used for complex scientific calculations in fields such as climatology, astronomy, and particle physics.

A MOSFET has four semiconductor terminals, called the source, gate, drain, and body. The source and drain are located in the body of the transistor, while the gate is above these three terminals, positioned between the source and drain. The gate is separated from the other terminals by a thin layer of insulation.

A MOSFET can be designed to use either negatively charged electrons or positively charged electron holes as electric charge carriers. The source, gate, and drain terminals are designed to have an excess of either electrons or electron holes, giving each a negative or positive polarity. The source and drain are always the same polarity, and the gate is always the opposite polarity of the source and drain.