| 摘要 |
PURPOSE:To improve the breakdown-strength characteristic of an oxide film, by intermittently supplying material gas, and laminating and forming a plurality of polycrystalline silicon layers, in which the diameters of crystal grains in each layer gradually increase toward an upper region from a lower region. CONSTITUTION:Monosilane is intermittently supplied in two times, end a polycrystalline silicon film is formed. This film is divided into two layers, i.e., an upper polycrystalline silicon layer and a lower polycrystalline silicon layer. Namely, the crystal growth in the upper layer is performed again independently from the crystal growth in the lower layer. Therefore, the diameter of the crystal grain in the upper layer becomes smaller than that in the conventional grain. An oxide film, which is formed on said polycrystalline silicon film, is formed in the upper polycrystalline silicon layer. Then the interface between the polycrystalline silicon and the oxide film is positioned in a region, in which the diameter of the crystal grain is small. The degree of asperity appearing at the interface becomes small. Thereby, the breakdown strength of the oxide film 1 can be improved.
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