Patent ID: 8134180

Claim:
A nitride semiconductor device comprising: a semiconductor base layer made of a conductive group III nitride semiconductor having a principal plane defined by an m-plane or an a-plane; an insulating layer formed on the principal plane of the semiconductor base layer with an aperture partially exposing the principal plane; a nitride semiconductor multilayer structure portion, formed on a region extending onto the insulating layer from the aperture, having a surface that includes a parallel surface parallel to the principal plane of the semiconductor base layer, and a +c-axis side first inclined surface and a −c-axis side second inclined surface inclined with respect to the principal plane of the semiconductor base layer, the nitride semiconductor multilayer structure portion including two types of group III nitride semiconductor layers each having different lattice constants; a gate electrode formed on and to be opposed to the second inclined surface; a source electrode arranged to be electrically connected with the group III nitride semiconductor layers; and a drain electrode formed on a back surface of the semiconductor base layer opposite to the principal plane.