Patent ID: 7638819

Claim:
A compound semiconductor device having a transistor configuration comprising: a substrate; a buffer layer formed on the substrate; and an electron supplying layer containing AlGaN formed on the buffer layer; wherein the buffer layer having a first buffer layer containing AlN formed on the substrate, a third buffer layer containing AIGaN formed on the first buffer layer, a second buffer layer containing GaN formed on the third buffer layer, the third buffer layer having a thickness within the range of 10 nm to 200 nm and formed to directly contact with the first buffer layer and the second buffer layer; and wherein an amount of Ga holes is within the range of 1×10 12 /cm 3 to 1×10 18 /cm 3 and a carbon concentration is within the range of 1×10 13 /cm 3 to 1×10 18 /cm 3 in the second buffer layer.