Thereafter, as illustrated in FIG. 5C, a back-face portion of the semiconductor wafer 30 is removed by a method such as chemical etching, back-face polishing, plasma etching or a method using these techniques so that the thickness of the semiconductor wafer is reduced to the range from about 30 ??m to about 150 ??m, both inclusive, thereby separating the semiconductor chips 2 from each other.