A semiconductor device includes a thyristor disposed in a semiconductor body. The thyristor has an anode, a cathode, a first bipolar transistor located on an anode side, and a second bipolar transistor located on a cathode side. The first and second bipolar transistors are nested and connected between the anode and the cathode. A MOS transistor is disposed in the semiconductor body. The MOS transistor is coupled between a collector region and an emitter region of the second bipolar transistor. The MOS transistor has a gate region connected to the cathode via a resistive semiconductor region that incorporates at least a part of a base region of the second bipolar transistor.