Patent ID: 7956383

Claim:
A field effect transistor, comprising: a first nitride semiconductor layer; a second nitride semiconductor layer formed on the first nitride semiconductor layer and having a wider bandgap than the first nitride semiconductor layer; a third nitride semiconductor layer formed on the second nitride semiconductor layer, the first, second and third nitride semiconductor layers being formed on a plane perpendicular to a (0001) plane or a plane tilted with respect to the (0001) plane; a source electrode and a drain electrode formed so as to contact at least a part of the second nitride semiconductor layer or the third nitride semiconductor layer; a gate electrode provided between the source electrode and the drain electrode in the third nitride semiconductor layer and formed in a recess that exposes a part of the second nitride semiconductor layer; and an insulating film formed between the third nitride semiconductor layer and the gate electrode, wherein the insulating film is formed between the second nitride semiconductor layer and the gate electrode at the recess, and the insulating film is made of SiN.