In this chapter we discuss two types of field-effect transistors: the junction field-effect transistor, JFET, and the insulated-gate field-effect transistor, IGFET, or more commonly, MOSFET (Metal-Oxide-Silicon Field-Effect Transistor). JFETs and MOSFETs are sometimes called unipolar transistors because only majority carriers take part in the conduction process, while in bipolar transistors both majority and minority carriers are involved in transistor action. Conduction in JFETs and MOSFETs occurs within a region called the channel. When the conduction carriers are electrons, the transistor is referred to as an N-channel JFET or MOSFET. In case of holes, the transistor is called a P-channel transistor. Complementary Field-Effect Transistors are N-channel and P-channel FETs designed and processed with similar characteristics but opposite polarities on the same chip. In the case of MOSFETs, the pair is referred to as Complementary Metal-Oxide-Silicon, CMOS.