| 摘要 |
PURPOSE:To suppress the uniformity of an impurity distribution in case of oxidizing and to reduce the leakage current of an oxide film on a polycrystalline silicon by setting oxidizing conditions to a high temperature and a short time by a momentarily heating method when a thermal oxide film is formed on a polycrystalline silicon pattern. CONSTITUTION:A first polycrystalline silicon film 3 is deposited, one of phospho rus, arsenic and boron is added in high concentration, its surface is then oxi dized, the surface is processed with diluted fluoric acid or ammonium fluoride, and a second polycrystalline silicon film 3' is formed. After the polycrystalline silicon film of the two layers is patterned, the upper face and the sidewall of a polycrystalline silicon pattern 3'' are momentarily thermally oxidized by a heating method or the like, and an insulating film 5 is formed. Thus, an impurity added in high concentration to the first layer 3 is diffused in the polycrystalline silicon of the second layer 3', and the polycrystalline silicon of the second layer 3' is reduced in its concentration. Thus, it can prevent the thermal oxide film of the lower part of the sidewall from decreasing in thickness than that of the upper face and the upper part of the sidewall, thereby reducing a leakage current of the oxide film. |
