Patent ID: 8004037

Claim:
An MOS type semiconductor device comprising: a semiconductor substrate having a first conductivity type low impurity concentration drift layer, second conductivity type base regions and first conductivity type high impurity concentration emitter regions laminated in ascending order on the semiconductor substrate; channel-forming region surfaces provided in a surface of the semiconductor substrate so as to be partially located between a surface of the drift layer and surfaces of the emitter regions; and stripe-like gate electrodes provided on the channel-forming region surfaces through gate insulating films respectively; wherein the emitter regions and the base regions are provided in a principal surface layer of the semiconductor substrate between the channel-forming region surfaces so that the emitter regions are in contact with the channel-forming region surfaces; second conductivity type stripe-like contact regions having higher impurity concentration than the base region, the contact regions being spaced from the gate insulting films, and the contact regions are exposed in centers of the principal surface located between the emitter regions; wherein the contact regions are separated into island-shaped surface patterns in such a manner that the emitter regions in contact with both sides of each of the contact regions are partially connected to each other to form ladder-shaped surface patterns; wherein a main electrode is in contact with the island-shaped contact regions and the ladder-shaped emitter regions in common so that the island-shaped contact regions and the ladder-shaped emitter regions are short-circuited in a surface of the main electrode; and wherein partial missing portions are provided in the ladder-shaped surface patterns of the emitter regions so that the island-shaped surface patterns of the contact regions exposed in the centers of the principal surface between the channel-forming region surfaces are formed as patterns which are connected along the principal surface and to at least one-side channel-forming region surfaces at portions corresponding to the missing portions so as to reach the outside of the emitter region.