NOVELTY - A source gas supply unit supplies source gas containing organic silane compound to reaction chamber (2) in which substrate (21) is mounted. A thin film is formed on the substrate by CVD process, in chemical vapor deposition (CVD) section (3). The source gas containing organic silane compound and hydrocarbon is used and thin film with desired composition ratio of silicon and carbon atoms is formed. The source gas and carrier gas are supplied to the chamber.    USE - Thin-film forming apparatus e.g. thermal chemical vapor deposition (CVD) apparatus, plasma CVD apparatus, gas shower type plasma CVD apparatus, reel type thermal CVD apparatus, roller type plasma CVD apparatus and roller type thermal CVD apparatus, for forming thin film used for negative-electrode material for lithium ion battery (claimed), channel layer for thin film transistor (claimed) and electric power generation layer for solar cell (claimed). The lithium ion battery is used for portable device such as notebook personal computer (PC) and mobile phone.    ADVANTAGE - The thin film can be formed safely and at low cost. The raw material solution can be vaporized easily. The size of the battery can be reduced. The performance of thin-film transistor and solar cell can be improved.    DETAILED DESCRIPTION - The thin-film forming apparatus (1) has raw material solution flow path that supplies solution containing organic silane compound to carrier gas flow-path (42). A heater heats and vaporizes raw material solution dispersed in carrier gas. The plasma generator applies plasma to reaction chamber. The plasma frequency is controlled and film with desired composition is formed. A temperature controller controls temperature in reaction chamber. The thin film with desired crystallinity is formed by controlling temperature in chamber. An INDEPENDENT CLAIM is included for thin-film formation method that involves selecting the kind of organic silane compound in source gas supplied to reaction chamber. The composition ratio of silicon and carbon atoms of the film is changed. A coating film tape is moved in the chamber using a moving device and a film is formed on the tape.    DESCRIPTION OF DRAWING(S) - The figure shows the schematic view of the thermal CVD apparatus.    Thin-film forming apparatus (1)    Reaction chamber (2)    CVD section (3)    Substrate (21)    Vaporization mechanism (40)    Carrier gas flow-path (42)