MANUFACTURING METHOD FOR THIN FILM

PROBLEM TO BE SOLVED: To provide a technology for the entire low-temperature process, especially when an epitaxial layer is grown on a silicon substrate surface. SOLUTION: A high-vacuum atmosphere formation process is provided, where the inside of a reaction chamber 12 in which a silicon substrate is provided, is evacuated to 1×10-6Pa, so that internal water content and oxygen are sufficiently removed. Then a surface treating process is provided, where a mixed gas containing silane gas and hydrogen gas is guided into the reaction chamber 12 with a naturally oxidized film on the silicon substrate surface and impurities being reduced and removed. Thus, the mixed gas of silane gas and hydrogen gas sufficiently reaches the silicon substrate surface for constant progress of reducing/removing reaction. So, even at a process temperature equal to 750 deg.C or lower which is lower than before, since a naturally oxidized film and impurities are sufficiently removed and all processes are performed at a temperature lower than conventionally problems related to sagging in distribution will not take place which has been caused so far by dispersion or auto-doping in a high-temperature atmosphere.