Method of making a semiconductor device with conductors on stepped substrate having planar upper surfaces
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United States of America Patent
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Feb 11, 1997
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N/A
app pub date -
Mar 1, 1995
filing date -
Apr 13, 1993
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Abstract
An element separating oxide film is formed on a P-type semiconductor substrate by means of a selective oxidation method, and then a gate oxide film is formed on the element separating oxide film by a thermal oxidation method. A gate electrode film made of an N-type polysilicon material is formed so as to extend along a step portion of the element separating oxide film on the semiconductor substrate. The upper surface of the gate electrode film is flattened by means of a surface polishing method. Then, isotropic etching is performed by using a resist pattern as a mask, thereby forming a gate electrode. Since in the method the upper surface of the gate electrode film in the flattened, the semiconductor substrate is prevented from being subject to over-etching when a gage electrode is formed, so that the changes of characteristics of MOS transistors are prevented whose gate insulative films have been becoming thinner as their elements have been finer.
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