| 摘要 |
PURPOSE:To readily form an extra-fine field oxide film by utilizing a lateral spread by converting a second polycrystalline silicon film into a second insulating film, ion implanting high density oxygen to a fine field region, and improving the oxidizing velocity only on the region. CONSTITUTION:A window is opened at a second oxide film 5 by reactive ion etching by a normal method, thermally oxidized in combustion oxidative atmosphere to convert the film 5 into a second insulating film 12. Then, a window is opened at a oxidation resistant film 4, and an inversion preventing impurity 8 is implanted into a silicon substrate 1 through the window. Then, it is coated with a photoresist film 6, opened with a window, and ion implanted with oxygen impurity 13. The films 6, 12 are removed, with the film 4 as a mask a field oxide film 9 is formed by thermally oxidizing in the substrate 1. The impurity 6 forms a field inversion preventing layer 10 by the heat treatment. Then, the films 4, 3 are removed, and an impurity is diffused in an element region partitioned by the film 9.
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