Semiconductor device

A semiconductor device comprising:

• A semiconductor substrate having an upper surface and a lower surface and provided with a drift region of a first conductivity type;
• an emitter electrode provided above the upper surface of the semiconductor substrate;
• a plurality of trench portions provided on the upper surface of the semiconductor substrate and arranged spaced from each other in an array direction;
• and
• a plurality of mesa portions sandwiched between each of the plurality of trench portions inside the semiconductor substrate, wherein
• the plurality of trench portions include a gate trench portion to which a gate voltage is applied,
• one mesa portion of two mesa portions in contact with the gate trench portion among the plurality of mesa portions is an active mesa portion in which an emitter region of the first conductivity type having a doping concentration higher than that of the drift region is arranged in contact with the gate trench portion,
• an other mesa portion of the two mesa portions in contact with the gate trench portion is a dummy mesa portion not having the emitter region, and
• a current-voltage change rate characteristic indicating a relationship between a collector current flowing through the semiconductor device and a voltage change rate of a collector-emitter voltage when the semiconductor device is turned on includes:
• a peak portion in which the voltage change rate exhibits a local maximum value;
• and
• a maintaining and increasing region in which the voltage change rate is maintained or increased in a direction in which the collector current is increased from the peak portion.