Manufacturing method of microcrystalline silicon film and manufacturing method of thin film transistor

Abstract

An object is to provide a manufacturing method of a microcrystalline silicon film with improved adhesion between an insulating film and the microcrystalline silicon film. The microcrystalline silicon film is formed in the following manner. Over an insulating film, a microcrystalline silicon grain having a height that allows the microcrystalline silicon grain to be completely oxidized by later plasma oxidation (e.g., a height greater than 0 nm and less than or equal to 5 nm), or a microcrystalline silicon film or an amorphous silicon film having a thickness that allows the microcrystalline silicon film or the amorphous silicon film to be completely oxidized by later plasma oxidation (e.g., a thickness greater than 0 nm and less than or equal to 5 nm) is formed. Plasma treatment in an atmosphere including oxygen or plasma oxidation is performed on the microcrystalline silicon grain, the microcrystalline silicon film, or the amorphous silicon film, so that a silicon oxide grain or a silicon oxide film is formed over the insulating film. A microcrystalline silicon film is formed over the silicon oxide grain or the silicon oxide film.