Semiconductor device with field stop layer and semiconductor device manufacturing method thereof

Abstract

First and second n-type field stop layers in an ndrift region come into contact with a pcollector layer. The first n-type field stop layer has an impurity concentration reduced toward an nemitter region at a steep gradient. The second n-type field stop layer has an impurity concentration distribution in which impurity concentration is reduced toward the nemitter region at a gentler gradient than that in the first n-type field stop layer and the impurity concentration of a peak position is less than that in the impurity concentration distribution of the first n-type field stop layer. The impurity concentration distributions of the first and second n-type field stop layers have the same peak position. The first and second n-type field stop layers are formed using annealing and first and second proton irradiation processes which have the same projected range and different acceleration energy levels.