A semiconductor device includes a semiconductor layer having a front surface on which a transistor is provided and a back surface opposite to the front surface, and a conductive member that penetrates through the semiconductor layer. In the semiconductor device, between a second plane including the back surface and a third plane, a solid material that is an insulator is provided between the conductive member and the semiconductor layer, and, between a first plane including the front surface and the third plane, a hollow part is provided between the conductive member and the semiconductor layer, and a center of the hollow part in a direction crossing the first plane and the second plane is positioned between the first plane and the third plane.