surface 22 having the orientation of 100 is exposed then referring to fig5 d the single crystal silicon bar 271 is sliced to provide semiconductor wafers 21 by the above described process a semiconductor wafer 21 having first and second notches 23 and 24 serving as marks for identifying the crystal orientation lt 110 gt is manufactured particular effects of this embodiment will be described in the following as shown in fig1 the first and second notches 23 and 24 are v shaped so that the vertices 25 and 26 are defined unequivocally accordingly the line 27 coupling the bottom portions 25 and 26 indicating the crystal orientation of the semiconductor wafer 21 is defined uniquely consequently in accordance with this embodiment the crystal orientation of the semiconductor wafer 21 can be indicated exactly in this embodiment the line 27 coupling the vertices 25 and 26 indicates the specified crystal orientation of the semiconductor wafer 21 compared with a case in which notches are provided such that a line coupling the both bottom portions intersect by a predetermined angle with the specified crystal orientation of the semiconductor wafer alignment in lithography is facilitated the line 27 coupling the vertices 25 and 26 has approximately the same length as the diameter of the circle defining the outer periphery of the semiconductor wafer 21 in this embodiment it is longer than a common orientation flat therefore alignment for lithography can be carried out more precisely when a semiconductor wafer having an orientation flat is thermally processed the semiconductor wafer may possibly be warped since the outer periphery of the semiconductor wafer does not expand uniformly.