| 摘要 |
PURPOSE:To increase the strength of gate insulation breakdown by a construction wherein a gate insulating film is, when preparing a MOS semiconductor device, provided in such a way that an insulating film produced in the diffusing region is allowed to remain, before being incorporated with the insulating film used for a mask, and then the mask insulating film in the diffusing region is removed to provide such the insulating film therein. CONSTITUTION:An insulating film 21 such as SiO2 is attached to the surface of an N type Si substrate, and a hole is made to attach N type impurities to the exposed substrate 20, which are heat-treated and diffused to form an N type region 22. Simultaneously, a relatively thick SiO2 film 21' linked with a film 21 is allowed to be produced on the surface. Next, the film 21' is made to remain without removing it, but only the initial film 21 in the region 22 is removed to make the boundary between the films 21 and 21' generate difference in level. A thin gate insulating film 21'' is attached to the exposed substrate 20 again in the region 22 on which a gate electrode is formed. In this way, the strength of gate insulation breakdown is improved without increasing the number of processes. |
