PURPOSE: To easily form a thin metallic or metallic oxide film on a substrate with a simple apparatus in simple stages by coating the substrate with a fluid of an org. substance contg. a dispersed or bonded and arranged metal and by carrying out plasma treatment to volatilize the org. substance.

CONSTITUTION: A film 2 of a fluid of an org. substance contg. a metal such as a polymer contg. dispersed or molecularly bonded and arranged Si is formed on a substrate 1 of a semiconductor, an insulator or the like by spin coating. The substrate 1 is then placed in a plasma treating apparatus 3, where H2 or O2 plasma treatment is carried out with an electrode 4. By this plasma treatment, a thin film 5 of a metal such as Si or a metallic oxide such as SiO2 is formed on the surface of the substrate 1 at a relatively low temp.