Patent ID: 8563984

Claim:
A semiconductor device having a configuration in which an active layer having a composition represented by a chemical formula: Al x M y Ga 1-x-y N in which 0≦x<1, 0≦y<1, 0≦x+y<1, and wherein M contains at least one of In and B, is formed on a conductive gallium nitride (GaN) substrate via a buffer layer and operates with current flowing through the active layer in the direction parallel to the surface of the substrate, wherein the buffer layer has a composition represented by a chemical formula: Al p M q Ga 1-p-q N and includes: a substrate connection region where p=q=0 which is formed on the side contacting the substrate in the thickness direction thereof; an active layer connection region where p=x and q=y which is formed on the side contacting the active layer in the thickness direction; and a high Al composition region with higher resistivity compared to the substrate, wherein 1≧p>x and 1>q≧0, which is formed between the substrate connection region and active layer connection region in the thickness direction.