Wiring substrate and manufacturing method thereof

A wiring substrate comprising:

• a plurality of insulating layers including an outermost insulating layer;
• and
• a plurality of wiring layers which are alternately laminated between the insulating layers and include
• outermost wiring layers exposed from the outermost insulating layer, and
• through wirings having electrode pads on end portions of the through wirings and penetrating through the outermost insulating layer,
• wherein the electrode pads of the through wirings are exposed from the outermost insulating layer, and
• a part of the outermost wiring layers overlaps the end portions of the through wirings and is connected to the through wirings,
• wherein exposed faces of the through wirings and faces opposite to the exposed faces of the through wirings are circular, and
• diameters of the exposed faces are smaller than diameters of the opposite faces of the through wirings,
• wherein at least one through wiring of the through wirings contacts an upper surface and side surfaces of an end part of the outermost wiring layers,
• wherein the outermost insulating layer contacts an upper surface and side surfaces of parts of the outermost wiring layers other than the end part so that the parts of the outermost wiring layers are embedded in the outermost insulating layer.