PURPOSE: To efficiently form a thin film consisting of the compd. of a solid component and a gaseous component on the surface of a solid by injecting a gas contg. reactive elements on the surface of a solid sample kept at high temp. from a nozzle.

CONSTITUTION: A solid sample 7 (e.g. silicon wafer) is vertically held in a reaction tube 2 horizontally arranged in an electric furnace 1. A nozzle tube 3 with the tip contracted is inserted into the reaction tube 2 along the center axis of the reaction tube 2. The sample 7 is heated to a high temp. by the high-frequency coil 1A of the electric furnace and kept at that temp., a gas 4 (e.g. gaseous oxygen) contg. reactive elements is supplied to the nozzle tube 3 and injected from its tip, and the jet is blown against the surface of the sample 7 kept at a high temp. Consequently, a thin film (e.g. silicon oxide film) consisting of the compd. of at least one component of the sample 7 and the gas 4 is formed on the surface of the sample 7.