| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor device which can prevent fluctuations of the potential of adjacent circuit regions caused by a surge voltage and can hold normal operation of an inner circuit, etc., with improved reliability. SOLUTION: Circuit regions 5 and 7 surrounded by trench groove insulating regions 9 and 10 are formed in a p-type silicon layer 2 of an SOI substrate 1, and an LDMOS 6 and an MOSFET 8 are formed in the circuit regions 5 and 7. A p-type silicon region 11 is formed between the insulating regions 9 and 10, a p-type diffusion layer 12 is provided on the surface of the p-type silicon region 11, an n-type diffusion layer 13 is provided at a position contacted with the insulating region 9 on the side of the circuit region 5, and the p- and n-type diffusion layers 12 and 13 are connected to a grounding terminal V0. As a result, an inversion layer is formed at a site of the p-type silicon region 11 in contact with the insulating region 9 to prevent a surge voltage in the circuit region 5 from being transmitted to the circuit region 7.
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