Patent ID: 7608864

Claim:
A semiconductor device, comprising: a semiinsulating substrate; a layered structure of compound semiconductor, which is provided on said semiinsulating substrate as a mesa structure, and contains an active channel layer as an intermediate layer, said mesa structure having a pyramid shape with a rectangular base; first and second metal main electrodes, which are provided on an upper surface of said mesa structure being away from each other in a channel length direction on an upper surface of said mesa structure and extending down along respective sides of said mesa structure so as to have inclined portions relative to said substrate; a metal control electrode provided between the first metal main electrode and the second metal main electrode; and first and second ion implantation regions, which are provided at edge sections of said mesa structure between said first and second metal main electrodes, facing each other in a channel width direction, and extending from an upper surface of said mesa structure to a depth level below said active channel layer, said first ion implantation region and said second ion implantation region being situated under the metal control electrode and away from the first metal main electrode and the second metal main electrode, wherein said first and second ion implantation regions isolate said active channel layer from said metal control electrode so as to prevent said metal control electrode from contacting said active channel layer.