| 摘要 |
PURPOSE:To form oxide films in each section in prescribed thickness with excellent reproducibility, and to obtain desired characteristics by adopting a selective etching method when forming a semiconductor device with field-effect transistor elements in which the gate oxide films having different thickness are shaped on the same semiconductor substrate. CONSTITUTION:P<+> layers 12a, 12b and 13a, 13b, which form mutually independent elements and each function as sources and drains, are formed on an N type substrate 11, a thick oxide film 14 is shaped on the whole surface, holes for several element are bored, and oxide films 15 are formed to each gate section. Sections except a gate section for the second element are coated with a photo- resist 17, and a thinner gate oxide film 15 is shaped through selective etching while using the photo-resist as a mask. In a semiconductor device acquired in this manner, high withstanding-voltage characteristics are obtained in the elements in thick gate oxide-film thickness, and the oxide films in prescribed thickness can be formed with high accuracy because of few oxidation processes, thus obtaining stable threshold voltage. High-frequency operation is enabled by acquiring the element with the thinner oxide film. |
