| 摘要 |
PURPOSE:To prevent a device from dielectric breakdown by a method wherein a diode with a breakdown voltage determined by a relative position of a buried layer for isolation with an element buried layer is formed as a protective element. CONSTITUTION:One conductivity type buried layer 3 and the other conductivity type buried layer 4 are formed on the one conductivity type semiconductor substrate 1. And the other conductivity type epitaxial layer 2 is built thereon and the one conductivity type isolation diffusion region 5 is formed in such a manner that its surface is level with that of the epitaxial layer 2 and its bottom is in contact with the one conductivity type buried layer 3 so that the region 5 isolates a part of the epitaxial 2 from the other part. Moreover, a diode with a breakdown voltage determined by a relative position 7 of the other conductivity type buried layer 3 with the one conductivity type buried layer 4 is formed as a protective circuit. The said diode is high in breakdown voltage, and therefore an NPN transistor 6 is protected against a high voltage. By these processes, an element is prevented from breakdown due to high voltage depending on static electricity or the like.
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