The Full Form of IGFET is Insulated-gate field-effect transistor.

The Insulated-Gate Field-Effect Transistor (IGFET), also known as the Metal Oxide Field Effect Transistor (MOSFET), is a derivative of the field effect transistor (FET). Today, most transistors are of the MOSFET type as components of digital integrated circuits. Though discrete BJT’s are more numerous than discrete MOSFET’s. The MOSFET transistor count within an integrated circuit may approach hundreds of a million. The dimensions of individual MOSFET devices are under a micron, decreasing every 18 months. Much larger MOSFET’s are capable of switching nearly 100 amperes of current at low voltages; some handle nearly 1000 V at lower currents. These devices occupy a good fraction of a square centimeter of silicon. MOSFET’s find much wider application than JFET’s. However, MOSFET power devices are not as widely used as bipolar junction transistors at this time.