Patent ID: 7635877

Claim:
A nitride semiconductor device for a field effect transistor, the nitride semiconductor device comprising: a first nitride semiconductor layer made of a III-V group nitride semiconductor material which is formed of a III group element made of at least one from among the group consisting of gallium, aluminum, boron and indium, and a V group element including at least nitrogen from among the group consisting of nitrogen, phosphorous and arsenic, and that has been deposited on a substrate; a second nitride semiconductor layer made of an undoped III-V group nitride semiconductor material which is formed of a III group element made of at least one from among the group consisting of gallium, boron and indium, and a V group element including at least nitrogen from among the group consisting of nitrogen, phosphorous and arsenic, and that has been deposited on the first nitride semiconductor layer and of which the film formation temperature is lower than that of said first nitride semiconductor layer such that the second nitride semiconductor layer has a crystallinity with crystallites; and an electrode that makes ohmic contact with the second nitride semiconductor layer which has a crystallinity with crystallites; and wherein said second nitride semiconductor layer is formed with a recess therein exposing said first nitride semiconductor layer for a control electrode to make Schottky contact with said first nitride semiconductor layer through said recess.