NOVELTY - Manufacture of semiconductor device comprises isolating vacuum chamber and air from each other, providing substrate (50) in vacuum chamber covered with bag, and forming semiconductor film (61) on the substrate. The step of isolating vacuum chamber and air comprises covering an outer wall of vacuum chamber with a bag. The step of forming semiconductor film comprises introducing source gas in the vacuum chamber, and generating plasma. One of noble gas and hydrogen gas is introduced in a space between air and outer wall of the vacuum chamber.    USE - Method for manufacturing semiconductor device (claimed) such as photoelectric conversion device typified by solar cell and sensor, and electro-optical device typified by LCD panel or electronic device with LED.    ADVANTAGE - The method reduces the leakage from outside of the chamber to the inside of the chamber, maintaining the inside of the chamber to be at less than or equal to 1/1000 of oxygen concentration and nitrogen concentration than those in the air, and provides space with high air tightness thus provides high purity of argon gas to bag. The method reduces production cost while providing higher yield.    DETAILED DESCRIPTION - The space has positive pressure greater than atmospheric pressure. The space is in contact with the outer wall of vacuum chamber. The semiconductor film is microcrystalline semiconductor film. The method involves forming gate electrode on substrate with insulating surface, forming insulating film over gate electrode, and forming buffer layer on microcrystalline semiconductor film. In forming the microcrystalline semiconductor film, a deposition condition is change step-by-step or continuously so that a deposition rate in a first region in a vicinity of interface with the buffer layer is greater. An INDEPENDENT CLAIM is included for film deposition apparatus.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross sectional view of manufacturing of semiconductor device.    Substrate (50)    Gate electrode (51)    Insulating films (52a-52c)    Semiconductor film (61)    Source and drain electrodes (71a-71c)    Buffer layer (73)    Insulating film (76)