| 摘要 |
PROBLEM TO BE SOLVED: To prevent leakage and short-circuiting between source and drain. SOLUTION: A semiconductor substrate 104 is composed of first and second semiconductor layers 106 and 110 composed of p-type silicon and an insulating layer 108. A MOS transistor 112 including a source 114, a drain 116, and a gate 120 is formed on the second semiconductor layer 110. N-type regions 4 are locally formed in the surficial area of the first semiconductor layer 106 in such positions that the n-type regions are opposite to the source 114 and the drain 116 of the transistor 112 with the insulating layer 108 between. Thus, even if minute holes 130 are formed through the source 114 or the drain 116 and the insulating layer 108 when contact holes 126 are formed by etching, and contact plugs 128 are short-circuited to the first semiconductor layer 106, diodes 6 arising from the n-type regions 4 are reversely biased and problems, such as short-circuiting between source and drain, do not arise.
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