Load-short-circuit-tolerant semiconductor device having trench gates

A semiconductor device comprising:

• a first-conductivity-type collector layer along a x-y plane defined by a x-direction and a y-direction which are orthogonal to each other;
• a second-conductivity-type drift layer formed on a front side of the collector layer;
• a first-conductivity-type base layer formed on the drift layer;
• trench gates including trenches extending in the y-direction to form a pattern of stripes, the trenches extending from a surface of the base layer along the x-y plane to an inside of the drift layer by penetrating the base layer in a z-direction orthogonal to the x-y plane, the trench gates further including a gate insulation layer formed on walls of the trenches and a gate electrode formed on the gate insulation layer;
• a second-conductivity-type emitter layer formed in a surface portion of the base layer and located on a side of the trench gates;
• a collector electrode formed on a back side of the collector layer and electrically connected to the collector layer;
• and
• an emitter electrode electrically connected to the emitter layer and the base layer, wherein
• the trench gate includes a bottom portion located in the drift layer and a communication portion extending from the surface of the base layer to communicate with the bottom portion,
• a distance between adjacent bottom portions in the x-direction is smaller than a distance between adjacent communication portions in the x-direction,
• the gate insulation layer is thicker in the bottom portion than in the communication portion,
• a region between adjacent trench gates is divided into an effective region and an ineffective region in the y-direction,
• the effective region corresponds to the emitter layer and serves as an injection source for injecting charges into the drift layer when a voltage is applied to the gate electrode,
• the ineffective region does not serve as the injection source even when the voltage is applied to the gate electrode, and
• an interval L1 (>0) of the ineffective region in the y-direction, a length D1 of the communication portion in the z-direction, and a length D2 of the bottom portion in the z-direction satisfy the following relationship:
• L1≦2(D1+D2).