Patent ID: 8248116

Claim:
A semiconductor device comprising: a reverse conducting semiconductor device including an IGBT element domain and a diode element domain coexisting in a mutual semiconductor substrate, wherein in the IGBT element domain, a second conductive type body region, a first conductive type drift region, and a second conductive type collector region are laminated, a first conductive type emitter region is formed on a surface of the body region, and a first trench gate electrode penetrating the body region that separates the emitter region from the drift region is formed, in the diode element domain, a second conductive type body region, a first conductive type drift region and a first conductive type drift contact region are laminated, a first conductive type first body contact region and a second conductive type second body contact region are formed on a surface of the body region, and a second trench gate electrode penetrating the body region that separates the first body contact region from the drift region is formed; a first gate voltage applying circuit controlling a voltage applied to the first gate electrode; and a second gate voltage applying circuit controlling a voltage applied to the second gate electrode, wherein each of the first and second gate voltage applying circuits applies a first voltage to at least the first trench gate electrode in a case where the IGBT element domain is maintained in an on-state, and applies a second voltage to at least the second trench gate electrode in a case where return current flows in the diode element domain, when the first voltage is higher than that of the body region, then the second voltage is higher than that of the body region, and when the first voltage is lower than that of the body region, then the second voltage is lower than that of the body region, and the first and second gate voltage applying circuits are composed of one single gate voltage applying circuit.