A semiconductor device, which comprises an insulated gate bipolar transistor and incorporates a freewheeling diode in antiparallel connection, comprising: a semiconductor substrate, and an emitter electrode provided above an upper surface of the semiconductor substrate, wherein the semiconductor substrate has: a first conductive type drift region, a second conductive type base region provided between the drift region and the upper surface of the semiconductor substrate, a first conductive type emitter region provided between the base region and the upper surface of the semiconductor substrate, wherein the first conductive type emitter region has a higher doping concentration than the drift region, a second conductive type contact region with a higher doping concentration than the base region, which is provided between the base region and the upper surface of the semiconductor substrate, a trench contact of a conductive material provided to connect to the emitter electrode, and a second conductive type high-concentration plug region with a higher doping concentration than the contact region, wherein the second conductive type high-concentration plug region is provided in contact with a bottom portion of the trench contact, wherein the trench contact is provided to penetrate the contact region and the emitter region from the upper surface of the semiconductor substrate, and to penetrate and directly contact part of the base region, wherein in a depth direction of the semiconductor substrate, a thickness of the high-concentration plug region is less than a thickness of the contact region and a lower end of the high-concentration plug region is arranged above a lower end of the base region so that the high-concentration plug region is only in contact with the base region and not in contact with the contact region and with the emitter region. a semiconductor substrate, and an emitter electrode provided above an upper surface of the semiconductor substrate, wherein the semiconductor substrate has: a first conductive type drift region, a second conductive type base region provided between the drift region and the upper surface of the semiconductor substrate, a first conductive type emitter region provided between the base region and the upper surface of the semiconductor substrate, wherein the first conductive type emitter region has a higher doping concentration than the drift region, a second conductive type contact region with a higher doping concentration than the base region, which is provided between the base region and the upper surface of the semiconductor substrate, a trench contact of a conductive material provided to connect to the emitter electrode, and a second conductive type high-concentration plug region with a higher doping concentration than the contact region, wherein the second conductive type high-concentration plug region is provided in contact with a bottom portion of the trench contact, wherein the trench contact is provided to penetrate the contact region and the emitter region from the upper surface of the semiconductor substrate, and to penetrate and directly contact part of the base region, wherein in a depth direction of the semiconductor substrate, a thickness of the high-concentration plug region is less than a thickness of the contact region and a lower end of the high-concentration plug region is arranged above a lower end of the base region so that the high-concentration plug region is only in contact with the base region and not in contact with the contact region and with the emitter region. a first conductive type drift region, a second conductive type base region provided between the drift region and the upper surface of the semiconductor substrate, a first conductive type emitter region provided between the base region and the upper surface of the semiconductor substrate, wherein the first conductive type emitter region has a higher doping concentration than the drift region, a second conductive type contact region with a higher doping concentration than the base region, which is provided between the base region and the upper surface of the semiconductor substrate, a trench contact of a conductive material provided to connect to the emitter electrode, and a second conductive type high-concentration plug region with a higher doping concentration than the contact region, wherein the second conductive type high-concentration plug region is provided in contact with a bottom portion of the trench contact, wherein the trench contact is provided to penetrate the contact region and the emitter region from the upper surface of the semiconductor substrate, and to penetrate and directly contact part of the base region, wherein in a depth direction of the semiconductor substrate, a thickness of the high-concentration plug region is less than a thickness of the contact region and a lower end of the high-concentration plug region is arranged above a lower end of the base region so that the high-concentration plug region is only in contact with the base region and not in contact with the contact region and with the emitter region.