In a semiconductor device, in addition to a first emitter layer, a second emitter layer is formed on the surface side of a p-type base in spaced-apart relation with the first emitter layer. The first emitter layer is the source region of a first MOSFET, while the second emitter layer is the source region of a second MOSFET. Through signals imparted to first and second gate electrodes, the device, when turned on, operates with a low on-voltage in a thyristor state and, when turned off, undergoes a turn-off in a short time by changing to a transistor state. The main current in the transistor state flows by being offset toward the first emitter layer side with respect to a main-current path on the lower side of the second emitter layer in the thyristor state. Since the current paths in each mode are separated, it is possible to reduce the resistance in the current path in the transistor state without increasing the on-voltage, thereby making it possible to obtain a large latch-up withstanding capacity. IMAGE
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