A crystal growing apparatus comprises a vacuum vessel, a heating lamp, a lamp controller for controlling the heating lamp, a gas inlet port, a flow rate adjuster for adjusting the flow rate of a gas, a pyrometer for measuring the temperature of a substrate, and a gas supply unit for supplying a Si2H6 gas or the like to the vacuum vessel. An apparatus for ellipsometric measurement comprises: a light source, a polariscope, a modulator, an analyzer, a spectroscope/detector unit, and an analysis control unit for calculating &PSgr;, &Dgr;. In removing a chemical oxide film on the substrate therefrom, in-situ ellipsometric measurement allows a discrimination between a phase 1 during which a surface of the substrate is covered with the oxide film and a phase 2 during which the surface of the substrate is partially exposed so that the supply of gas suitable for the individual phases is performed and halted.