| 摘要 |
PURPOSE:To easily control the film thickness of two kinds of devices formed on an identical substrate by a method wherein, after nitrogen ion has been implanted rapidly into a region to form a low-voltage operating device on the substrate, two device-forming regions are treated simultaneously by a thermal oxidation process. CONSTITUTION:A region A, where a MOS transistor for a low-voltage operating circuit is formed by a device isolation film 2, and a region B, where another MOS transistor of a high-voltage operating circuit is formed, are formed on a silicon semiconductor substrate 1. Then, nitrogen ion is implanted into the region A and controls the target film thickness of a silicon oxide film. Then, this assembly is heat-treated a gate oxide film 10 whose film thickness is thin is formed on the region A and another gate oxide film 11 whose film thickness is thick is formed in the region B. After that, polycrystalline silicon films 6 acting as gate electrodes are formed on the films 10, 11 impurities are diffused into the substrate 1 then source regions 7 and drain regions 6 are formed. |
