Patent ID: 8390030

Claim:
A semiconductor device comprising: a first semiconductor layer made of Al x Ga 1−x N (0≦x<1); a second semiconductor layer provided on the first semiconductor layer and made of undoped or first conductivity type Al y Ga 1−y N (0<y≦1,x<y); an anode electrode and a cathode electrode which are connected to the second semiconductor layer; and a third semiconductor layer of second conductivity type provided between the anode electrode and the cathode electrode when viewed from a direction perpendicular to an upper surface of the second semiconductor layer, the third semiconductor layer being provided in a current pathway between the anode electrode and the cathode electrode, the third semiconductor layer being not connected electrically to the anode electrode and the cathode electrode and the third semiconductor layer being electrically floating, the third semiconductor layer being depleted when a predetermined magnitude or more of voltage is applied between the anode electrode and the cathode electrode.