Patent ID: 8350292

Claim:
A gallium nitride type epitaxial crystal for field effect transistor, comprising: a base substrate, (a) a gate layer, (b) a high purity first buffer layer containing a channel layer contacting an interface on the base substrate side of the gate layer, (c) a second buffer layer arranged on the base substrate side of the first buffer layer, (d) a non-gallium nitride type insulating layer arranged on the base substrate side of the second buffer layer, and having an opening at a part thereof, and (e) a p-conductive type semiconductor crystal layer arranged on the base substrate side of the insulating layer and connected to a hole-withdrawing electrode that is provided at an exposed part of the p-conductive type semiconductor crystal layer, wherein a connection layer is arranged in the opening of the non-gallium nitride type insulating layer to electrically connect the first buffer layer and the p-conductive type semiconductor crystal layer, and wherein said connection layer is a p-conductive type crystal comprising a group III-V type crystal.