Next, as illustrated in FIGS. 9A to 9C, the columnar body CL2 and the second stacked body 2 are etched to divide the initial columnar body CL2i at the substantially center thereof in the X direction by using a lithography technique and an etching technique. An insulating film is buried in the slit to form the first division insulating film 50. Accordingly, the first division insulating film 50 is formed to divide the initial columnar body CL2i at the substantially center thereof in the X direction. That is, as illustrated in FIG. 9A, in a planar shape of the hole SH2, the initial columnar body CL2i is divided so that the first division insulating film 50 passes the substantially center of the initial columnar body CL2i. It is preferable that the left and right areas of the columnar body CL2i after the division are substantially equal. For example, silicon oxide is used for the first division insulating film 50. It is noted that FIG. 9B illustrates a cross section along the F-F line of FIG. 9A, and FIG. 9C illustrates a cross section along the G-G line of FIG. 9A.
