Patent ID: 8330187

Claim:
A GaN-based field effect transistor, comprising: a substrate; a channel layer comprised of p-type or undoped GaN-based compound semiconductor material formed on the substrate; an electron supply layer formed on the channel layer and comprised of GaN-based compound semiconductor material, the electron supply layer having bandgap energy greater than that of the channel layer; a drift layer between the electron supply layer and the channel layer, comprising p-type or undoped GaN-based compound semiconductor material, the drift layer having bandgap energy smaller than that of the electron supply layer and impurity concentration lower than that of the channel layer; a surface layer formed on the electron supply layer and comprised of GaN-based compound semiconductor material, the surface layer having bandgap energy smaller than that of the electron supply layer; a first recess section having a surface of the channel layer as a bottom surface, exposed by removing a part of the surface layer, the electron supply layer and the drift layer; an insulating film formed on the surface layer and an inner surface of the first recess section; a gate electrode formed on the insulating film in the first recess section; and a source electrode and a drain electrode electrically connected to the channel layer, the source electrode and the drain electrode being formed on respective sides of the gate electrode, on a surface of the electron supply layer in a second recess section and a third recess section respectively formed in the surface layer and on a same level.