Patent ID: 6936870

Claim:
A heterojunction type compound semiconductor field effect transistor comprising: a channel layer provided on a compound semiconductor substrate and composed of intrinsic GaAs or InGaAs; a first electron supply layer provided on the channel layer and composed of AlGaAs doped with n type impurities; an electric field strength reducing layer provided on the first electron supply layer and composed of intrinsic InGaP; a first contact layer provided on the electric field strength reducing layer and composed of GaAs or InGaAs doped with n type impurities; a recess stopper layer provided on the first contact layer and composed of intrinsic InGaP; a second contact layer provided on the recess stopper layer and composed of GaAs doped with n type impurities of a concentration higher than that of the first contact layer; a wide recess opening formed to penetrate the second contact layer so as to expose a surface of the recess stopper layer; a narrow recess opening formed in the wide recess opening to penetrate the recess stopper layer, the first contact layer, and the electric field strength reducing layer so as to expose a surface of the first electron supply layer; a gate electrode provided on the surface of the first electron supply layer exposed from a bottom of the narrow recess opening; and a source electrode and a drain electrode provided on the second contact layer outside the wide recess opening so that the wide recess opening is sandwiched between the source electrode and the drain electrode.