MULTILAYER WIRING SUBSTRATE

PROBLEM TO BE SOLVED: To solve the problem that simultaneous switching noise is increased and a fault product is produced in a multilayer wiring substrate in which semiconductor elements are mounted in a high density and are operated at a high speed. SOLUTION: The multilayer wiring substrate comprises an insulating substrate 2 formed by sequentially laminating a plurality of insulating layers 2a to 2e and wiring layers 4 to 6, connecting electrodes 8 of the semiconductor elements 9 provided on the upper surface of the substrate 2, external electrodes 7 provided on the lower surface to supply power to the elements 9, a plurality of through conductors 20 formed through openings 21 provided in the layers 4 to 6 and 23 therein in such a manner that planar shapes of the adjacent openings 21 and sectional shapes of the conductors 20 are elliptical, and the openings 21 and the conductors 20 are aligned and arrayed in a minor axis direction of the elliptical shape. Since current routes 22 of the wiring layers 4 to 6 and 23 can be assured between the openings 21, an inductance component can be reduced, and a gap between the conductor 20 and the wiring layers 23 via the opening 21 can be increased.