| 摘要 |
PURPOSE:To form a fine semiconductor device easily subject to stable gm by a method wherein a polysilicon oxide film and a gate oxide film of MOSFET are simultaneously formed on the same Si substrate. CONSTITUTION:A P well 22 and an N well 23 are provided on a P type Si substrate 21; the P well 22 is encircled by a P<+>type layer 26; and an Si3N4 mask 25 is used to selectively form SiO2 film 27. The other SiO2 film 38 and the first polySi 29 are newly over-lapped on the substrate 21 to be doped with phosphorus. First, a gate oxide film 38a and a polySi oxide film 38b are simultaneously formed by photoetching process and thermal oxidizing process. Second, a gate electrode and a capacity electrode are formed of the second polySi thin films 31 and then the static capacity element interior device in polySi structure is completed by conventional process. In such a constitution, a semiconductor device can be formed stably with high precision without increasing the thickness of gate oxide film initially formed due to the effect of simultaneous formation subject to no decline in gm.
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