| 摘要 |
In a conventional semiconductor device, there is a problem that an N-type diffusion region provided for protecting an element from an overvoltage is narrow and a breakdown current is concentrated so that a PN junction region for protection is broken. In a semiconductor device of the present invention, an N-type buried diffusion layer is formed across a substrate and an epitaxial layer. A P-type buried diffusion layer is formed across a wider region on an upper surface of the N-type buried diffusion layer so that a PN junction region for overvoltage protection is formed. A P-type diffusion layer is formed so as to be connected to the P-type diffusion layer. A breakdown voltage of the PN junction region is lower than a breakdown voltage between a source and a drain. With this structure, the concentration of the breakdown current is prevented so that the semiconductor device can be protected from the overvoltage.
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