METHOD OF DIVIDING WAFER AND METHOD OF MANUFACTURING SEMICONDUCTOR DEVICE

PURPOSE: A wafer dividing method and a semiconductor device manufacturing method is provided to be capable of decreasing the degree of chipping on the rear side of wafers and preventing a decrease in breaking strength of chips. CONSTITUTION: Grooves(22) are formed in a surface(21') of a wafer(21), on which semiconductor elements are formed, along dicing lines or chip parting lines on the wafer(21). The grooves(22) are deeper than the thickness of a finished chip, and each of them has a curved bottom surface. A holding sheet is attached on the surface of the wafer on which the semiconductor elements are formed. Subsequently, the rear surface of the wafer is lapped and polished to the thickness of the finished chip, thereby dividing the wafer into chips. Even after the wafer is divided into the chips, the lapping and polishing is continued until the thickness of the wafer becomes equal to the thickness of the finished chip. The lapping and polishing amount(A) required to attain the thickness of the finished chip after the lapped face of the wafer(21) reaches the bottom surface of the groove(22), and a depth(B) of a region of the curved bottom surface of the groove(22) defines a ratio(A/B) of not less than 0.3.