Semiconductor Device

Abstract

To provide a semiconductor device by which oscillation at turn-off time can be prevented effectively.SOLUTION: An n-type first buffer layer 110 between a first principal face MS1 of a semiconductor substrate 101 and an n-type drift layer 190 includes: a first region 111 adjacent to the drift layer 190, containing a proton; a second region 112 adjacent to the first region 111, containing a proton and located between the first region 111 and the first principal face MS1; and a third region 113 between the second region 112 of the first buffer layer 110 and the first principal face MS1. An impurity concentration profile of the first buffer layer 110 has: a maximum value in the second region 112, as its maximum; a folding-bending part at a boundary point KN of the first region 111 and the second region 112, where decrease from the maximum value is eased or stopped; and as the third region 113, a distribution of a range of 5 μm or larger, and of impurity concentration configured of values equal to or larger than 80% of the maximum value at the boundary point and equal to or smaller than 5.0×1014 / cm3 below the value at the boundary point.SELECTED DRAWING: Figure 2