Patent ID: 7919790

Claim:
A semiconductor device comprising: a semiconductor substrate of a first conductivity serving as a first semiconductor layer of the first conductivity type having a first principal surface and a second principal surface; a second semiconductor layer of a second conductivity type having a higher impurity concentration than the first semiconductor layer and in contact with at least part of the first semiconductor layer on the first principal surface of the first semiconductor layer; a third semiconductor layer of the first conductivity type having a higher impurity concentration than the first semiconductor layer and on a side of the second principal surface of the first semiconductor layer; a first electrode in contact with at least part of the second semiconductor layer; and a second electrode in contact with at least part of the third semiconductor layer, wherein the first semiconductor layer includes at least one region where the impurity concentration is locally maximized so that the impurity concentration thereof decreases from the locally maximized region toward both the second and third semiconductor layers, and wherein a carbon concentration of the semiconductor substrate is in a range of 6.0×10 15 to 2.0×10 17 atoms/cm 3 , both inclusively.