| 摘要 |
PURPOSE:To obtain a high-reliability oxide film by restraining the variation of an impurity concentration and shortening the oxidation time by performing a two-step oxidation in which a low-temperature oxidation is effected at first and a high-temperature oxidation next when oxidizing plural regions of different concentrations simultaneously. CONSTITUTION:A diffusion region 2 is arranged near the surface of a substrate 1 and openings 3 and 4 for forming an oxide film on said diffusion region 2 and the surface of the substrate 1 are formed. When the openings 3 and 4 are desired to be oxidized simultaneously, these are oxidized slightly, at first, at low temperature of such a degree that out-diffusion and auto-doping do not occur, thereby forming a cap oxide film 5. The temperature at this time is 900 deg.C or lower and the film thickness is 50Angstrom or under. For forming the cap oxide film 5, thermal oxidation is not always required. A wet treatment using acid or alkali is available and also the oxidation due to excitation with light or plasma can be applied. Next, a high-temperature oxidation is performed to form a main oxide film 6.
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