| 摘要 |
PURPOSE:To make it possible to implement an oxide film, whose thickness is equal to or smaller than that of a gate oxide film, on polycrystalline silicon, by implanting nitrogen ions into a first polycrystalline silicon layer, and forming an electrode layer on the oxide film, which is formed by thermal oxidation. CONSTITUTION:A specified amount of nitrogen ions are implanted 4 in a first polycrystalline silicon layer 3. Thereafter, the first polycrystalline silicon layer 3, which is an electrode beneath a capacitor, is oxidized at the same time when a gate oxide film 6 is formed. An oxide film for a capacitor is formed end its thickness is controlled in correspondence with the amount of the implantation of the nitrogen ions. Thus a thin oxide film 5 can be formed on the first polycrystalline silicon layer 3. Since the thickness of the oxide film can be controlled in a broad range, the design of the capacitor, which is formed at the same time as a transistor, becomes easy, and the area of the capacitor can be made small.
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