| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor device having an ESD protection circuit in which a gate insulating film exhibits a high breakdown voltage and high durability. SOLUTION: The semiconductor device comprises an MOS transistor supplying a surge current between a source and a drain in order to protect a main circuit wherein the MOS transistor has a first conductivity type well 2 of a first impurity concentration formed on the surface of a semiconductor substrate 1. A gate electrode 13 connected electrically with ground potential is provided on a gate insulating film 12 arranged on the surface of the well. The source region and the drain region 15 are formed on the surface of the well so as to sandwich a channel region beneath the gate electrode while having a second conductivity type opposite to the first conductivity type wherein one of them is connected electrically with the ground potential thus constituting the source and the drain. A first conductivity type first impurity diffusion region 16 is formed along a plane facing the channel region of the source region and the drain region and has a second impurity concentration higher than the first impurity concentration. COPYRIGHT: (C)2005,JPO&NCIPI
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