GaN-based FET has a sapphire substrate of about 50 nm thick on which an
n-type GaN electron transit layer and an Al0.2Gao0.8N electron
supply layer are formed, together with n+-type GaN contact regions sandwiching
the electron transit and supply layers therebetween. On the entire faces of these
layer and regions is formed a polyimide interlayer insulating film of about 3000
nm thick that is formed with contact holes in which source, drain and gate electrodes
are formed, each of which is comprised of a TaSi/Au layer and about 5000 nm in
thickness. The source and drain electrodes are ohmic-connected to the n+-type
GaN contact regions and the gate electrode is in contact with an SiO2
gate insulating film.
