If the thinnest dummy insulating film described above is formed on the semiconductor surface in the pad opening 16 c in the process shown in FIG. 1D, the area where the thinnest dummy insulating films are formed in the sixteen wafer periphery pad areas PD shown in FIG. 4A is 16S where S is an area where the thinnest dummy insulating film is formed in one pad area shown in FIG. 6A. The area where t