PURPOSE: To provide a titled device which solves the problem of residual potential and forms a homogeneous and improved deposited film by constituting the device in such a manner that the distances between the respective gas release ports of a gaseous raw material introducing pipe and gaseous halogen oxidizing agent introducing pipe and substrate can be respectively independently changed.

CONSTITUTION: The distance between the quartz glass substrate 118 imposed on a substrate holder 112 in a vacuum vessel 120 and a gas release port support 111 is set and further, the distances (a), (b), (c) between the gas release ports 104'W106' and the support 111 are respectively set at desired values. After the inside of the vessel 120 is evacuated 119 to a prescribed vacuum degree, the substrate is heated 113 up to a desired temp. Gaseous SiH4 101 is introduced 104 into the vessel 120 and simultaneously, gaseous F2 102 diluted with gaseous He and gaseous B2H6 103 diluted with the gaseous He are introduced 105, 106 into the vessel 120. This state is maintained for the prescribed time by which an Si:H:F film is deposited on the substrate 18. Since there is no chance for the electric discharge to be induced in the reaction chamber with the device of this invention, the deposited film to be formed is kept free from undesirable influences of ion damage and others such as abnormal discharge effect.