Patent ID: 7781786

Claim:
A semiconductor device comprising: a heterojunction diode configured by a first semiconductor region, and a second semiconductor region having a band gap different from that of the first semiconductor region and forming a heterojunction with the first semiconductor region; and an avalanche breakdown region in which an impurity density is equal to or less than a predetermined value, provided in a portion or entirety of the second semiconductor region, the predetermined value being a value of impurity density such that a dielectric breakdown electric field of the second semiconductor region is the same as the first semiconductor region, wherein the heterojunction is arranged such that when a predetermined reverse bias is applied to the heterojunction diode, a breakdown voltage at least in a heterojunction region other than outer peripheral ends of the heterojunction diode is a breakdown voltage of the semiconductor device, the breakdown voltage is determined by a voltage caused by avalanche breakdown, and when the predetermined reverse bias is applied to the heterojunction diode, the avalanche breakdown is caused in the avalanche breakdown region.