A semiconductor device includes first and second semiconductor components mounted on an interposer mounted on a wiring substrate, and electrically connected to each other via the interposer. Also, a plurality of wiring layers of the interposer include first, second and third wiring layers which are stacked in order from a main surface side to be a reference. In addition, in a first region of the interposer sandwiched between the first semiconductor component and the second semiconductor component, a ratio of a reference potential wiring in the third wiring layer is higher than a ratio of a reference potential wiring in the first wiring layer. Further, in the first region, a ratio of a signal wiring in the first wiring layer is higher than a ratio of a signal wiring in the third wiring layer.