US Patent 7432531 Semiconductor device

A semiconductor device, which can accurately control carrier density, includes: a single crystal substrate; a semiconductor layer which is made of hexagonal crystal with 6 mm symmetry and is formed on the single crystal substrate; a source electrode, a drain electrode and a gate electrode which are formed on the semiconductor layer, where the main surfaces of a GaN layer and an AlGaN layer constituting the semiconductor layer respectively include C-axis of the hexagonal crystal, and a length direction of a channel region in the semiconductor layer is parallel to the C-axis of the hexagonal crystal.