A semiconductor device, includes: a first semiconductor chip including: a first substrate; a first via; a first rear surface-side pad connected to the first via; a first wiring layer; a first front surface-side pad formed on the first wiring layer; and an input circuit formed in the first substrate, an input signal wire connecting the first via, the first front surface-side pad, and an input terminal of the input circuit; and a second semiconductor chip including: a second substrate; a second wiring layer; a second front surface-side pad; and an output circuit formed in the second substrate, an output signal wire connecting the second front surface-side pad to an output terminal of the output circuit. The second semiconductor chip is stacked on a rear surface side of the first semiconductor chip, and the first rear surface-side pad and the second front surface-side pad are connected.