Patent ID: 8426892

Claim:
A compound semiconductor device comprising: a buffer layer formed on a conductive SiC substrate; an i-type GaN-based carrier transit layer formed on the buffer layer; a carrier supply layer formed on the carrier transit layer; a source electrode and a drain electrode formed on the carrier supply layer; and a gate electrode formed on the carrier supply layer between the source electrode and the drain electrode, wherein the buffer layer includes a first AlN layer formed on the conductive SiC substrate; a second AlN layer formed on the first AlN layer; and an Al x Ga 1-x N layer formed on the second AlN layer, in which a transition metal element is added, and in which the Al composition x is 0≦x≦1, wherein a first surface between the first AlN layer and the second AlN layer has greater textured roughness than a second surface between the conductive SiC substrate and the first AlN layer; wherein the textured roughness has a plurality of tips of different heights.