PURPOSE: To preferably embed and to reduce roughness of a surface of a workpiece by heating the workpiece to a temperature adapted for filling a part to be filled in a first step, and heating the workpiece to a temperature adapted for morphology of a thin film in a second step.

CONSTITUTION: A heating lamp is turned ON to indirectly heat a wafer 10 through a wafer mounting base 3. Thus, the wafer 10 rapidly rises at its temperature. After the temperature of the wafer 10 becomes about 425°C, treated gas is supplied to a treating chamber 2 via a treated gas supply tube 21 while maintaining the temperature. After this film forming step is conducted, the supply of the gas is stopped, power of the lamp 4 is regulated to increase its irradiation amount, thereby raising the temperature of the wafer to about 475°C. Thereafter, supply of the gas is started to form a film.