a metal interconnection layer and a hole for a device contact plug not shown may be formed in cell region a 1 as shown in fig4 15 in order to create the bonding pad structure for bonding pad 350 in bonding pad region a 2 u2033 a plurality of holes for a plurality of bonding pad contact plugs 295 are formed the holes for bonding pad contact plugs 295 are preferably formed as having either a ring shape or a mesh shape note however that as the depth of a bonding pad contact hole increases it becomes more difficult to form a hole pattern into a mesh shape as shown in fig4 16 through 4 18 as the depth of the hole for bonding pad contact plug decreases such as that in bonding pad regions a 2 u2033 relative to that in bonding pad region a 2 u2032 it becomes easier to form the hole and tungsten plug 295 than to form the hole and tungsten plug 290 in bonding pad region a 2 u2032 in a subsequent manufacturing process the holes for bonding pad contact plugs 290 and 295 are preferably etched under a condition where an etching selection ratio of an oxide layer with respect to a polycrystalline silicon layer is high such that an etching process can be finished at the polycrystalline silicon layer after etching the holes for bonding pad contact plugs 290 and.