A semiconductor device including a substrate and first and second packages thereon, the first package includes a first lower redistribution layer; a first core semiconductor stack thereon and including a first core chip and a first through via stacked on the first lower redistribution layer; and a first memory semiconductor stack on the first lower redistribution layer and including first memory chips stacked on the first lower redistribution layer, the second package includes a second lower redistribution layer; a second core semiconductor stack thereon and including a second core chip on the second lower redistribution layer; and a second memory semiconductor stack on the second lower redistribution layer and including second memory chips stacked on the second lower redistribution layer, the first through via penetrates the first core semiconductor stack, and the first and second lower redistribution layers are electrically connected to each other through the first through via.