a i u2266 l if l u2266 a i u2266 2l then the quantity of defects d2 that accumulate is equal to d2 2r wl u03c0 a i l 2 when a 1 l a measurement of the effectiveness of a barrier structure is specified as the ratio of d2 to d1 denoted by where u03b1 w l if u03b4 is equal to 0 5 meaning that the barriers reduce the quantity of accumulated defects by a factor of two then u03b1 equals 0 785 so that l equals about 1 27 w if l is 1 5 or more times w the reliability of the interconnection around the through hole is improved by a factor of at least two the lower limit on the width w i e the spacing between the two insulating barriers 100 is determined by the maximum acceptable current density in the first interconnection layer the spacing w should be much smaller than the length a 1 along which the defects can move the maximum value of a 1 i e that defect moving length is several hundred microns although the length depends upon many conditions preferably the value of w is 1 5 to 1 10 of that maximum length namely less than about 30 microns in order to make the barriers effective in the embodiment of the invention shown in fig1 a and 13 b the two insulating barriers 100 are formed in grooves in the wide interconnection 13 in order to control the direction of the current flow in the vicinity of the through hole 16 however as shown in fig2 a and 20 b if the through hole 16 is disposed near the gap between the wide electrode 13 and the narrow electrode.