Abstract: A field effect transistor includes an active layer having a surface; a source electrode and a drain electrode disposed on the surface of the active layer; a first gate electrode disposed on the surface of the active layer between the source electrode and the drain electrode, having a T-shaped cross section, and a lower layer and an upper layer, the lower layer contacting the active layer, and the upper layer being disposed on the lower layer and having a lower resistivity than the lower layer, and being longer than the lower layer in the direction parallel to the gate length; and a second gate electrode disposed on the surface of the active layer between the first gate electrode and the drain electrode, having a rectangular cross section and a single layer. The gate resistance of the first gate electrode is reduced, whereby efficiency is improved and noise is reduced.

Abstract: A method for producing a semiconductor device includes preparing a semi-insulating substrate having an active layer, depositing a first insulating film on the active layer and forming two first openings in the first insulating film, depositing a second insulating film on the first insulating film filling the first openings and make a flat surface with the surface of the first insulating film, removing a portion of the first insulating film between the first openings to form a second opening, etching the active layer through the second opening formed by the removal of the first insulating film, removing parts of the second insulating film on opposite sides of the first insulating film from the active layer to form a third opening, and etching the active layer through the third opening formed by removal of the second insulating film to form a double-stage recess.