Wiring substrate having multiple build-up parts

A method for manufacturing a wiring substrate, comprising:

• forming a first build-up part comprising a plurality of first insulating layers and a plurality of first conductor layers, and a plurality of via conductors;
• and
• forming a second build-up part comprising a plurality of second insulating layers and a plurality of second conductor layers such that an outermost second insulating layer in the second build-up part is laminated on the first build-up part, that a minimum wiring width of wirings in the first conductor layers is smaller than a minimum wiring width of wirings in the second conductor layers, and that a minimum inter-wiring distance of the wirings in the first conductor layers is smaller than a minimum inter-wiring distance of the wirings in the second conductor layers,
• wherein the first build-up part is formed such that the first conductor layers and the via conductors includes a first layer and a second layer formed on the first layer, that the first layer and the second layer are integrally forming the first conductor layers and via conductors comprising the first layer and the second layer, that the plurality of first conductor layers includes an outermost first conductor layer embedded in the outermost second insulating layer in the second build-up part and integrally formed with at least one outermost via conductor, that the first layer in each of the via conductors is covering an inner wall surface in a respective via opening and has a first portion and a second portion electrically connected to the first portion, that the first portion has a portion formed closer to a center of the respective via opening than the second portion, and that the wirings in the first conductor layers have a minimum wiring width of 3 μm or less and a minimum inter-wiring distance of 3 μm or less.