Mesh holes 35a and 59a of upper solid layers 35 and upper solid layers 59 are formed to overlie on one another, so that the insulating properties of interlayer resin insulating layers 50 are not lowered. Here, the diameter of each mesh hole is preferably 75 to 300 .mu.m. The reason is as follows. If the diameter of the mesh hole is less than 75 .mu.m, it is difficult to overlay the upper and lower mesh holes on one another. If the diameter exceeds 300 .mu.m, the insulating properties of the interlayer resin insulating layers deteriorate. In addition, the distance between the mesh holes is preferably 100 to 2000 .mu.m. The reason is as follows. If the distance is less than 100 .mu.m, the solid layer cannot function. If the distance exceeds 2000 .mu.m, the deterioration of the insulating properties of the interlayer resin insulating film occurs.