| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem that impurity concentration at the surface of a silicon substrate becomes high because a p-type well layer is formed within an n-type well layer. SOLUTION: The first phosphorus ion implantation is performed to a p-type silicon substrate using a resist mask as the implantation mask to form a deep n-type well layer, and the n-type well layer is also formed simultaneously with the LOCOS oxidation. Next, the phosphorus ion implantation is performed in multiple stages using the resist mask to form the n-type well layer to surround a high concentration n-type well layer. Next, boron ion is implanted in multiple stages using the resist mask in order to form the p-type well layer. Thereafter, the heat treatment is carried out to form the n-type well layer up to the silicon substrate from the deep n-type well layer and also form the p-type well layer in the area surrounded by the n-type well layer. COPYRIGHT: (C)2003,JPO
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