A method includes: etching a target layer of a target object in a processing chamber by generating a plasma of a first gas containing at least one of SF6, ClF3 and F2 supplied into the processing chamber to; and forming a protective film on the target layer by generating a plasma of a second gas containing at least one of hydrocarbon, fluorocarbon, and fluorohydrocarbon supplied into the processing chamber. In the etching, a pressure in the processing chamber is set to a first pressure and a first bias power is applied to a lower electrode. In the forming, the pressure is set to a second pressure lower than the first pressure and a second bias power higher than the first bias power is applied to the lower electrode.