A method for separating a multiple number of semiconductor devices or semiconductor integrated circuits from a wafer on which the multiple number of semiconductor devices or semiconductor integrated circuits are formed is provided. The method includes forming a mask pattern on a surface of the wafer, and separating each of the semiconductor devices or semiconductor integrated circuits along the mask pattern formed on the surface of the wafer. The mask pattern is a repeated pattern without having a lattice line shape, and the step of separating each of the semiconductor devices or semiconductor integrated circuits is performed by plasma etching.