To form a gate electrode and a pad electrode without causing step breakage, by using an insulating film formed after element isolation as a spacer for lift-off during ohmic electrode formation.

An operation layer region is recess-etched through an opening 32 using a resist film 22 as a mask until it reaches a n-type AlGaAs electron supply layer 12-a. At this time, the n-type AlGaAs electron supply layer 12-a acts as a stopper during recess-etching, which enables uniform current control. In this recess-etching process, an opening 32 of the resist film 22 formed at the bottom of a mesa as well is also exposed to etchant. Since a SiN film 100 remains on the entire bottom of the mesa, however, GaAs at the bottom of the mesa will not be etched. Therefore, almost no step is produced between a gate electrode pattern and the bottom of the mesa. This makes it possible to form a gate electrode and a pad electrode without causing step breakage.