A semiconductor device in which an insulating material layer contains no reinforced fibers such as a glass cloth or a nonwoven cloth and which enables miniaturization of metal thin-film wiring layers, a reduction in the diameter of metal vias, and a reduction in interlayer thickness. The semiconductor device includes an insulating material layer including one or more semiconductor elements sealed with an insulating material containing no reinforced fibers, a plurality of metal thin-film wiring layers, metal vias that electrically connect the metal thin-film wiring layers together and electrodes of the semiconductor elements and the metal thin-film wiring layers together, and a warpage adjustment layer arranged on one principal surface of the insulating material layer to offset warpage of the insulating material layer to reduce warpage of the semiconductor device.