Wiring substrate

A wiring substrate, comprising:

• a first build-up part comprising a plurality of first insulating layers, a plurality of first conductor layers formed on the first insulating layers, and a plurality of first via conductors formed in the first insulating layers such that the first via conductors connect the first conductor layers;
• and
• a second build-up part laminated to the first build-up part and comprising a plurality of second insulating layers, a plurality of second conductor layers formed on the second insulating layers, and a plurality of second via conductors formed in the second insulating layers such that the second via conductors connect the second conductor layers,
• wherein the first and second build-up parts are formed such that a wiring width and an inter-wiring distance of wirings in the first conductor layers of the first build-up part are smaller than a wiring width and an inter-wiring distance of wirings in the second conductor layers of the second build-up part, and the first build-up part is formed such that the first insulating layers include insulating resin and inorganic particles and that the insulating resin in the first insulating layers forms surfaces of the first insulating layers covered by the first conductor layers.