A method for forming a functional silicon- or germanium-containing amorphous deposited film on a substrate which comprises a film-forming chamber having a film-forming space, a substrate holder and an electric heater for positioning the substrate in the film-forming chamber, an exhaust pipe in fluid communication with the film-forming chamber, a first gas-introducing portion for providing an active species (H), having an activation space for generating the active species (H), a microwave discharge supply source and a passage for providing a gaseous hydrogen-containing material into the activation space in order to produce the active species (H), a second gas-introducing portion for providing a gaseous silicon- or germanium-containing material (X), capable of reacting with the active species (H) to form a reaction product (HX) that is capable of forming the functional deposited film on the substrate, and a transportation path having a mixing space and a second microwave discharge energy supply source for promoting reaction with the active species.