Patent attributes
A main etching process of forming a recess portion in a multilayer film having a laminated film where a first film and a second film having different relative permitivities are alternately formed on a base silicon film to a preset depth and an over etching process of forming the recess portion until the base silicon film is exposed are performed by introducing a processing gas including a CF-based gas and an oxygen gas and by performing a plasma etching process. In the over etching process, a first over etching process where a flow rate ratio of the oxygen gas to the CF-based gas is increased as compared to the main etching process and a second over etching process where the flow rate ratio of the oxygen gas to the CF-based gas is reduced as compared to the first over etching process are repeatedly performed two or more times.
