METAL-oxIDE-SEMICONDUCTOR FET (MosFET) The principal difference between a metal-oxide-semiconductor FET (MOSFET) and a JFET is that the gate region is physically isolated from the channel region by means of a thin layer of silicon dioxide, eliminating the possibility of a gate current even with a forward biased gate-source junction. For this reason the MOSFET is also referred to as the insulated gate FET or IGFET. There are two types of Ts: the depletion-type (D-Mos) and the enhancement-type (E-MOS)