Patent ID: 8039871

Claim:
A semiconductor device comprising: a compound semiconductor substrate; a buffer layer, a channel layer, and a Schottky junction foaming layer sequentially laminated on said compound semiconductor substrate, each of said buffer layer, said channel layer, and said Schottky junction forming layer being a compound semiconductor; a source electrode and a drain electrode located on said Schottky junction forming layer; and a gate electrode disposed between said source and drain electrodes and forming a Schottky junction with said Schottky junction forming layer, wherein dopant impurity concentration within said channel layer varies in inverse proportion to the third power of depth in said channel layer, the depth in said channel layer being measured from a top surface of said channel layer toward said buffer layer, said top surface being located at an interface of said channel layer and said Schottky junction forming layer, said channel layer has a fixed dopant impurity content so that thickness of said channel layer varies inversely with the dopant impurity concentration of said channel layer at said top surface of said channel layer, and the dopant impurity concentration at said top surface of said channel layer is in a range from 5.0×10 17 cm −3 to 2.0×10 18 cm −3 .