A semiconductor device includes a first substrate having a first surface for mounting an electronic component and a second surface substantially parallel to the first surface. The first substrate includes a first region for mounting the electronic component, a second region including a plurality of first communication units for transmitting and receiving signals to and from a second substrate, input-output circuits disposed on the first region or the second region, the input-out circuits corresponding to the first communication units, and a control circuit for controlling input to and output from the input-output circuits disposed on the first region or the second region of the first substrate. Each of the input-output circuits includes an output circuit for outputting a signal to a second communication unit of the second substrate corresponding to the first communication unit and an input unit for receiving a signal sent from the corresponding second communication unit.