Patent ID: 6926934

Claim:
A deposited-film formation method comprising the steps of: providing a discharge electrode in a vacuum vessel equipped with exhaust means; supplying a hydrogen gas and a raw material gas for forming a deposited film which contains at least an Si element; generating plasma from the material gas by supplying high frequency electric power of 1 MHz to 200 MHz to the discharge electrode; and forming a deposited film on a substrate in the vacuum vessel by plasma CVD, wherein an auxiliary electrode electrically separate from said substrate is arranged in plasma spaced between the discharge electrode and the substrate in the vacuum vessel, and a periodically changing voltage having a voltage frequency of 1 MHz to 500 MHz and a maximum amplitude of 80V or less is applied to the auxiliary electrode, wherein a voltage lower than the potential of plasma is applied to the auxiliary electrode to avoid discharge and to form the deposited film while controlling generation of hydrogen radicals.