A wafer, in which a plurality of rectangular regions are defined on the face of the wafer by streets arranged in a lattice pattern, and a semiconductor memory element is disposed in each of the rectangular regions, is divided along the streets to separate the rectangular regions individually, thereby forming a plurality of semiconductor devices. Before the wafer is divided along the streets, a strained layer having a thickness of 0.20 .mu.m or less, especially 0.05 to 0.20 .mu.m, is formed in the back of the wafer. The strained layer is formed by grinding the back of the semiconductor wafer by a grinding member formed by bonding diamond abrasive grains having a grain size of 4 .mu.m or less by a bonding material.