After etching a polysilicon film, when a protective film made of a carbon polymer is formed on a sidewall of the polysilicon film using plasma containing carbons, a metallic material as a lower film is etched using plasma containing a halogen gas under an etching condition in which volatility is improved due to the rise in a wafer temperature or the low pressure of a processing pressure, thereby preventing a side etching and unevenness of a sidewall of the polysilicon film. Further, by using the protective film made of a carbon polymer, metallic substances scattered at the time of etching the metallic material are not directly attached to the polysilicon film, but can be simply removed along with the protective film made of a carbon polymer in an asking step.