Patent ID: 8222107

Claim:
A method of producing a semiconductor device, comprising: step (a) of implanting an impurity of a second conductivity type into a first semiconductor layer of a first conductivity type by using a first implantation mask layer, thereby forming a second conductivity-type semiconductor region in a surface region of the first semiconductor layer; step (b) of forming a second implantation mask layer covering the first implantation mask layer and the first semiconductor layer and having an opening for exposing a portion of the second conductivity-type semiconductor region, and implanting an impurity of the second conductivity type by using the first implantation mask layer and the second implantation mask layer, thereby forming within the second conductivity-type semiconductor region a second conductivity type high-concentration region having a higher concentration than an impurity concentration in the second conductivity-type semiconductor region; step (c) of forming a third implantation mask layer burying the opening, and thereafter selectively removing the second implantation mask layer; step (d) forming a fourth implantation mask layer on a side face of the first implantation mask layer and a side face of the third implantation mask layer; step (e) of implanting an impurity of the first conductivity type by using the first implantation mask layer, the third implantation mask layer, and the fourth implantation mask layer, thereby forming a first conductivity-type semiconductor region within the second conductivity-type semiconductor region; and step (f) of forming an electrically conductive layer in contact with the first conductivity-type semiconductor region and the second conductivity type high-concentration region, wherein, at step (e), the first conductivity-type semiconductor region is formed so as to surround the second conductivity type high-concentration region at an interval from an outer periphery of the second conductivity-type semiconductor region at any arbitrary depth of the first semiconductor layer, the method further comprising a step of, before step (e), removing the fourth implantation mask layer formed on the side face of the third implantation mask layer.