| 摘要 |
PURPOSE:To raise the interlayer insulating withstand voltage by a method wherein a thermal oxidation is performed on the first polycrystalline silicon layer and the substrate at low temperatures, whereby the oxide film is formed and after the oxide film on the substrate is removed, a thermal oxidation is performed at high temperatures and the interlayer insulating film and the second gate oxide film are formed. CONSTITUTION:Field oxide films 2, a first gate oxide film 3 and a first polycrystalline silicon layer 4 are formed in order on a single crystal silicon substrate 1. Then, an etching is performed on the first polycrystalline silicon layer 4 and the first gate oxide film 3, and by performing a vapor oxidation on the surface of the substrate 1 and the first polycrystalline silicon layer 4 at low temperatures, a polycrystalline silicon oxide film 6 and an oxide film 5 are formed. Then, when an etching is performed on the oxide film 5 and the polycrystalline silicon oxide film 6 to a degree that the substrate 1 is made to expose, the polycrystalline silicon oxide film 6 remains as the oxide film 6 is thicker than the oxide film 5. After this, when a thermal oxidation is performed at high temperatures, a second gate oxide film 7 is formed on the substrate 1, and at the same time, the polycrystalline silicon oxide film 6 becomes a thicker as the first polycrystalline silicon layer 4l is oxidized through the polycrystalline silicon oxide film 6. |
