Field effect transistor

摘要

A field effect transistor formed of a semiconductor of a III group nitride compound, includes an electron running layer formed on a substrate and formed of GaN; an electron supplying layer formed on the electron running layer and formed of AlxGa1-xN (0.01≦̸x≦̸0.4), the electron supplying layer having a band gap energy different from that of the electron running layer and being separated with a recess region having a depth reaching the electron running layer; a source electrode and a drain electrode formed on the electron supplying layer with the recess region in between; a gate insulating film layer formed on the electron supplying layer for covering a surface of the electron running layer in the recess region; and a gate electrode formed on the gate insulating film layer in the recess region. The electron supplying layer has a layer thickness between 5.5 nm and 40 nm.