Abstract: The present invention provides a film forming apparatus capable of removing a natural oxide film of a silicon substrate W at a very low temperature, as compared to the related art. The natural oxide film is removed at a low temperature by converting the natural oxide film on the silicon substrate W into a volatile material and evaporating the volatile material. The natural oxide film can be converted into volatile ammonium fluorosilicate by reaction with ammonium fluoride. A single crystal SiGe film can be grown on the silicon substrate W from which the natural oxide film is removed. The film forming apparatus includes an etching chamber, a SiGe growing chamber, and a substrate transport chamber that transports the silicon substrate in a controlled atmosphere.