Incidentally, ???one side??? and ???whether the angle ??1 or ??2 is the right angle??? as mentioned above are determined according to the state of occurrence of side erase shown in FIGS. 9A to 9C, more specifically conditions such as the region in which side erase occurs (that is, whether side erase occurs inward or outward relative to the exposed surface 20M) and the range in which side erase occ