Gan-based field effect transistor

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 said channel layer and comprised of GaN-based compound semiconductor material which has band gap energy greater than that of said channel layer;
• a surface layer formed on said electron supply layer and is comprised of GaN-based compound semiconductor material having band gap energy smaller than that of said electron supply layer;
• an insulating film formed on said surface layer and on inner surface of recess section having a surface of said channel layer that was exposed by removing a part of said surface layer and said electron supply layer as a bottom surface;
• a gate electrode formed on said insulating film of said recess section;
• and
• a source electrode and a drain electrode electrically connected to said channel layer and formed so that said gate electrode positions between them.