Method for formation of multilayer film

A method for forming a multilayer film by introducing a material gas into a reduced-pressure reaction chamber provided with a pair of parallel planer electrodes and supplying a high-frequency electric power to the electrodes thereby generating a plasma state therein and depositing a film on a substrate disposed on one of the electrodes, comprising the steps of (a) introducing a first material gas into the reaction chamber and supplying the high-frequency electric power to the electrodes thereby generating the plasma state and depositing a first film on the substrate, (b) introducing stepwise a preparatory gas and adjusting stepwise a distance between the electrodes, a pressure inside the chamber and a RF power supplied to the electrodes while continuously retaining the plasma state subsequently to step (a), and (c) introducing a second material gas into the reaction chamber while continuously retaining the plasma state thereby and depositing a second film on the first film. According to the method the surface between the films is desirably formed, and this cause a promotion of characteristics when applied to produce a multilayer films constitutes semiconductor device, a TFT and a solar cell for example.