Patent ID: 8575656

Claim:
A semiconductor device, comprising: a semiconductor substrate; a first semiconductor layer of a nitride provided directly on the semiconductor substrate or on the semiconductor substrate via a buffer layer; a second semiconductor layer of a nitride provided on the first semiconductor layer and having a band gap wider than that of the first semiconductor layer; a third semiconductor layer of a nitride provided so as to be spaced apart from the second semiconductor layer; a fourth semiconductor layer of a nitride provided on the third semiconductor layer and having a band gap wider than that of the third semiconductor layer; a fifth semiconductor layer of a nitride provided between the second semiconductor layer and the third semiconductor layer to insulate the second semiconductor layer and the third semiconductor layer from each other; a first electrode formed at least in a first opening extending from the fourth semiconductor layer to the fifth semiconductor layer to form an ohmic junction with the second to the fourth semiconductor layers; a second electrode provided on the fourth semiconductor layer to form an ohmic junction with the fourth semiconductor layer; a gate insulating layer, at least a portion of the gate insulating layer being formed in a second opening provided in the fourth semiconductor layer and being formed on the third semiconductor layer; a gate electrode provided on the gate insulating layer between the first electrode and the second electrode; and a third electrode to form a Schottky junction with the second semiconductor layer, the third electrode being provided so that the second electrode is interposed between the third electrode and the gate electrode, the third electrode being provided in a third opening extending from the third to the fifth semiconductor layer.