| 摘要 |
PROBLEM TO BE SOLVED: To make small both on-resistance and breakdown voltage variation in a semiconductor device containing a P-N junction. SOLUTION: An n-layer 2E of low impurity concentration is epitaxially grown to as far as the position of a depth D from a surface S1 of an n<+> Si substrate 1 of high impurity concentration. Phosphorus P is ion-implanted from the surface S1 into the n-layer 2E. After this, an SiO2 film 8 is formed on the surface S1 by thermal oxidation, and an opening 19 is formed in the SiO2 film. Further, a p-type impurity is implanted into the n-layer 2E after ion implantation by utilizing the opening, and the p-type impurity is diffused by a thermal treatment, so that a p-type diffused layer (well) is formed as far as to the position of a specified depth from the surface S1. As a result, an (n) layer provided with an impurity concentration distribution in which a monotonic decrease is shown from the side of the surface S1 and a minimum value is provide on an interface BS side is formed. After this, a specified electrode, etc. is formed to complete an element.
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