Patent ID: 7304331

Claim:
A nitride semiconductor device comprising: a non-doped first aluminum gallium nitride (Al x Ga 1-x N (0≦x≦1)) layer which is formed as a channel layer; a non-doped or n type second aluminum gallium nitride (Al y Ga 1-y N (0≦y 1, x≦y)) layer which is formed on the first aluminum gallium nitride layer as a barrier layer; an aluminum nitride (AlN) film which is formed on the second aluminum gallium nitride layer as a gate insulating film lower layer, the aluminum nitride film being selected from a polycrystalline film and an amorphous film; an aluminum oxide (Al 2 O 3 ) film which is formed on the aluminum nitride film as a gate insulating film upper layer; a source electrode and a drain electrode which are formed as first and second main electrodes to be electrically connected to the second aluminum gallium nitride layer, respectively; and a gate electrode which is formed on the aluminum oxide film as a control electrode.