1. A circuit substrate, comprising:a substrate having a first surface and a second surface opposite to the first surface, the substrate comprising:
a plurality of patterned pads disposed on the first surface of the substrate, and each of the patterned pads has a contact opening, wherein a wall surface of the contact opening is an inclined surface, and a diameter of the contact opening away from the first surface is larger than a diameter of the contact opening adjacent to the first surface;
a wire build-up layer structure disposed on the first surface of the substrate, the wire build-up layer structure comprising:
an interconnect build-up layer; and
a plurality of conductive pillars, the conductive pillars electrically connecting the interconnect build-up layer and the patterned pads, wherein each of the conductive pillars correspondingly abuts the inclined surface of the wall surface of each of the contact openings; and
an insulating layer disposed between the substrate and the wire build-up layer structure.