Method for manufacturing semiconductor device and plasma processing method

A method for manufacturing a semiconductor device that includes a stacked channel in which thin or sheet-shaped channels are stacked in a direction perpendicular to a substrate in a gate formation region, and that insulation-isolates a gate and a semiconductor substrate from each other by an insulating film,

• the semiconductor device having a structure in which a stacked film is provided in which a plurality of first semiconductor layers and a plurality of second semiconductor layers are alternately stacked on the semiconductor substrate, the gate and a gate sidewall spacer film are further formed on the stacked film, a part of the stacked film is removed by etching along the gate sidewall spacer film, and a part or all of a lowermost first semiconductor layer or a part or all of a lowermost second semiconductor layer formed on the lowermost first semiconductor layer are left without being etched, the method comprising:
• a first step of depositing a protective dielectric film on a sidewall of the stacked film including the first semiconductor layers and the second semiconductor layers that are formed by the etching;
• a second step of subjecting the protective dielectric film to anisotropic etching in a vertical direction to expose a surface of the lowermost first semiconductor layer or the lowermost second semiconductor layer;
• a third step of repeating the first step and the second step a plurality of times using a material of the insulating film different from that of the protective dielectric film, and forming, on the sidewall, a stacked film of protective dielectric films including the protective dielectric film and a plurality of protective dielectric films different from the protective dielectric film;
• and
• a fourth step of removing the lowermost first semiconductor layer or the lowermost first semiconductor layer and the lowermost second semiconductor layer by etching.