SEMICONDUCTOR DEVICE AND ITS MANUFACTURING METHOD

摘要

PURPOSE: To provide a semiconductor device improved in drain breakdown voltage. CONSTITUTION: This semiconductor device is constituted by forming a P-type well region 5 in a P-type semiconductor substrate 1, at least a thick gate insulating film 9 and a thin gate insulating film 10 on the region 5, and a gate electrode (25E) via the gate insulating films 9 and 10. The impurity injected into a portion below the electrode (25E) through ion implantation for adjusting threshold voltage is injected only into the lower part of the thick gate insulating film 10 in this invention.