| 摘要 |
PURPOSE:To improve insulating characteristics, by performing thermal oxidation under the state a CVD oxide film is present, and forming a thermal oxide film having a uniform thickness on the surface of a silicon layer having irregularities. CONSTITUTION:An insulating film 2 is formed on a silicon substrate 1. A CVD oxide film 3 is deposited, and a groove 4 is formed. Thereafter, an oxide film 3 is removed, and an oxide film 5 by a CVD method is deposited. Thermal oxidation is performed, and a thermal oxide film 6 is formed on the surface of the silicon substrate 1 beneath the CVD oxide film 5. At a corner A at the recessed part, oxidation speed is decreased owing to the concentration of stress at the thermal oxidation. As a result, the interface between the formed thermal oxide film 6 and the silicon substrate 1 becomes round. At a corner B at the protruded part, stress concentration is similarly formed. At this part, the amount of oxygen, which is diffused in the CVD oxide film 5 and supplied to the silicon substrate 1, is more than that in the flat part. Therefore, the effect of the decrease in oxidation speed can be compensated. Thus, the thermal oxide film 6 becomes thick, and the round part is effectively formed. Therefore, the thickness of the corner part of a thermal oxide film 7 as a capacitor insulating film, which is finally formed, does not become thin.
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