When the first wiring layer 212a is embedded in the first insulating layer 211a, a step generated due to a thickness of the first wiring layer 212a may be significantly reduced, and an insulating distance of the connection structure 240 may thus become constant. That is, a difference between a distance from a redistribution layer 242 of the connection structure 240 to an upper surface of the first insulating layer 211a and a distance from the redistribution layer 242 of the connection structure 240 to connection pads 221P and 222P of semiconductor chips 221 and 222 may be smaller than a thickness of the first wiring layer 212a. Therefore, a high density wiring design of the connection structure 240 may be easy.