| 摘要 |
PURPOSE:To provide a sufficiently thick buried layer by forming a buried layer of a first conductivity type on a lightly-doped substrate surface of a second conductivity type. CONSTITUTION:A pattern composed of a pad oxide film 12 and a nitride film 13 is formed on a p<+> silicon substrate 11, and this pattern is used as a mask to implant an n-type impurity 14 in high concentration. The impurity 14 is activated and diffused by a heat treatment to form an n<+> diffused layer 15 and a thermal oxide film 16. The nitride film 13 is then removed, and a p-type impurity 17 is implanted into the substrate 11. The impurity is activated and diffused by a heat treatment to form p-type diffused layers 18a and 18b. The oxide films 12 and 16 are removed from the surface of the substrate 11. A thick photoresist 19 is applied to cover the diffused layer 18b, and an n-type impurity 20 is implanted. The impurity 20 is activated and diffused by a heat treatment to form an n<+> buried layer 100 including an n<+> diffused layer 21 directly under the diffused layer 18a. The p-type diffused layer 18a is thus enclosed by the buried layer 100 and isolated from the substrate, and it has a sufficient thickness.
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