| 摘要 |
PURPOSE:To prevent a gate threshold voltage from being decreased due to the input of a high surge voltage, by providing a source region, a drain region and a gate insulation film in a region surrounded by thick-film element isolating regions while providing highly doped regions directly under the opposite ends of the gate insulation film. CONSTITUTION:A semiconductor substrate 1 is provided with a source region 4, a drain region 5 and a gate insulation film 3 which are formed in a region surrounded by thick-film element isolating regions 2 on the semiconductor substrate 1. The semiconductor substrate 1 is provided also with highly doped regions 8 having the same conductivity type as that of the substrate 1, directly under the opposite ends of the gate insulation film 3 adjacent to the thick-film element isolating regions 2. In this manner, decrease of a threshold voltage at the ends of the gate insulation film 3 is compensated very effectively and, thus, no current is leaked even if a high surge voltage is applied externally.
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