METHOD FOR ETCHING LAYER TO BE ETCHED.

Provided is a method for etching an etching target layer of a workpiece. The workpiece has a mask on the etching target layer. The etching target layer and the mask are formed from respective materials for which etching efficiency by a plasma of a rare gas having an atomic number greater than an atomic number of argon is higher than etching efficiency for the materials by a plasma of argon gas. The mask is formed from a material having a melting point higher than that of the etching target layer. The method includes (a) exposing the workpiece to a plasma of a first process gas containing a first rare gas having an atomic number greater than the atomic number of argon, and (b) exposing the workpiece to a plasma of a second process gas containing a second rare gas having an atomic number less than the atomic number of argon.