| 摘要 |
PROBLEM TO BE SOLVED: To increase the reverse breakdown voltage of a PN junction of a high voltage insulated-gate field-effect transistor by forming a low-concentration drain region of low impurity and a first conductivity low-concentration isolation region of low impurity, isolating them from each other. SOLUTION: On the surface of a P-type silicon substrate 1, an N+-type source region 2 and an N+-type drain region 3 are formed. Between the source region 2 and the drain region 3, a channel region 7 is formed. On the channel region 7, a gate electrode 9 of a polycrystalline silicon film is formed with a gate insulating film 8 of a silicon oxide film in between. Between the drain region 3 and the channel region 7, a low-concentration N+--type drain region 4 of low concentration is caused to exist. Besides, a field insulating film 5 is formed on the low-concentration drain region 4. To increase the breakdown voltage between the drain region 3 and the silicon substrate 1, an N--type WELL region 6 is formed in the periphery of the drain region 3.
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