| 摘要 |
PURPOSE:To keep an impurity concentration of a channel region to a low level and make it possible to have a high mobility of a gate oxide by forming the gate oxide film at a temperature which is lower than that of an epitaxial growth in the case of forming the channel region with a CVD technique when the gate oxide film is formed. CONSTITUTION:After forming an epitaxial growth layer 2, a substrate is set in a hot wall-type CVD device under reduced pressure. Dichlorosilane and dinitrogen monoxide are used as material gases to form a gate oxide film 3 and the excellent oxide film is obtained, for example, by keeping a substrate temperature at 850 deg.C and by setting a gas pressure and a gas flow rate at optimum conditions. In this way, an impurity diffusion is suppressed to the extent that its diffusion from a highly concentrated substrate 1 to a low concentrated epitaxial growth layer 2 is negligible and operations can be performed at great speed by forming the gate oxide film 3.
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