A semiconductor package and associated methods, the package including a substrate; first and second semiconductor chips on the substrate; and external terminals below the substrate, wherein the substrate includes a core portion; first and second buildup portions on top and bottom surfaces of the core portion, the first and second buildup portions including a dielectric pattern and a line pattern; and an interposer chip in an embedding region in the core portion and electrically connected to the first and second buildup portions, the interposer chip includes a base layer; a redistribution layer on the base layer; and a via that penetrates the base layer, the via being connected to the redistribution layer and exposed at a surface of the base layer, the redistribution layer is connected to a line pattern of the first buildup portion, and the via is connected to a line pattern of the second buildup portion.