Method of fabricating packaging substrate

A method of fabricating a packaging substrate, comprising:

• providing a carrier board having two opposite surfaces, on which a plurality of first conductive pads disposed for semiconductor chips to be disposed on the first respective conductive pads;
• forming first metal bumps on the first conductive pads, each of the first metal bumps having a first end and an opposite second end, wherein the second end is disposed on one of the first conductive pads;
• covering the surfaces of the carrier board, the first conductive pads and the first metal bumps with a first dielectric layer that has a plurality of first intaglios for exposing top and side surfaces of the first ends of the first metal bumps, respectively;
• forming a conductive seedlayer on the first dielectric layer and the first ends of the first metal bumps;
• forming a metal layer on the conductive seedlayer;
• removing a portion of the metal layer and the conductive seedlayer that is over a top surface of the first dielectric layer, and forming a first circuit layer in the first intaglios;
• forming a built-up structure on the first circuit layer and the first dielectric layer, an outermost layer of the built-up structure having second conductive pads for an external electronic device to be disposed on the second conductive pads;
• and
• removing the carrier board.