PURPOSE: To form a high quality epitaxial layer with superior uniformity, by introducing gas into a reaction chamber in the manner in which the partial pressure of gas state compound containing at least one element out of fluorine, chlorine and bromine becomes a specified value.

CONSTITUTION: A substrate 12 of boron-added P-type silicon is arranged on a graphite susceptor 13 covered with silicon carbide in a reaction vessel 11. Under the condition that the pressure in the reaction vessel 11 is lower than or equal to 1 Pa, the substrate 12 is heated by a tungsten-halogen lamp 14. Monosilane gas, hydrogen gas, fluorine gas, diborane gas and chlorine gas are introduced into the reaction vessel 11, through a gas nozzle 15 made of quartz glass. At this time, the partial pressure of gas state compound containing at least one element out of fluorine, chlorine and bromine is set lower than or equal to 10%. Thereby a high quality epitaxial layer can be formed at a low temperature, and a fine LSI element can be formed.