In one embodiment of the present invention, a multilayer wiring substrate includes: a first wiring substrate having a first core member made of metal with cavities therein; a second wiring substrate having a second core member made of metal; and a bonding layer between the first wiring substrate and the second wiring substrate to bond a top surface of the first wiring substrate to a bottom surface of the second wiring substrate, the bonding layer having a patterned conductive layer.