WIRING SUBSTRATE

A wiring substrate includes a first conductor layer including wirings, an interlayer insulating layer formed on the first conductor layer and covering the first conductor layer, a second conductor layer formed on the interlayer insulating layer and including wirings, a via conductor formed in the interlayer insulating layer such that the via conductor is penetrating through the interlayer insulating layer and connecting the first conductor layer and the second conductor layer, and a wiring part formed in the interlayer insulating layer and including an embedded wiring layer filling one or more grooves formed in the interlayer insulating layer. The interlayer insulating layer includes a first insulating layer and a second insulating layer laminated on the first insulating layer, and the embedded wiring layer is formed in the first insulating layer on a side facing the second insulating layer and filling the groove or grooves formed in the first insulating layer.