A semiconductor device equipped with a base board 10, a first element 20, a second element 30, and an interposer board 40, wherein: the first element 20 is positioned on the base board 10; a signal transmitting/receiving terminal 24 of the first element and a plurality of base board terminals 13 contact one another and are capable of transmitting and receiving a signal; the second element 30 is positioned on the base board 10; a signal transmitting/receiving terminal 34 of the second element and the plurality of base board terminals 13 contact one another and are capable of transmitting and receiving a signal; the interposer board 40 is positioned so as to extend on the first element 20 and the second element 30; a first contactless signal transmitting/receiving unit 43 of the interposer board is capable of contactlessly transmitting and receiving a signal to and from a contactless signal transmitting/receiving unit 25 of the first element via a first element board; and a second contactless signal transmitting/receiving unit 44 of the interposer board is capable of contactlessly transmitting and receiving a signal to and from a contactless signal transmitting/receiving unit 35 of the second element via a second element board 31.