| 摘要 |
A dual diffusion layer composed of an n- type diffusion layer 5 and an n+ type diffusion layer 6 is formed in a first element forming region element-separated by a field oxidized film 2, a p+ type diffusion layer 7 is formed in a second element forming region, a p type guard ring layer 3 provided below the field oxidized film 2 and the cathode n+ type diffusion layer 6 are placed adjacent to each other, and thus reach-through breakdown voltage is made lower than that of an internal transistor.
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