A semiconductor device including: a plurality of semiconductor units each constituting a three-level inverter circuit; and a connection unit electrically connecting the plurality of semiconductor units in parallel, wherein each of the semiconductor units includes: a multi-layer substrate including an insulating plate and circuit plates disposed on a primary surface of the insulating plate; a plurality of semiconductor elements each having a back surface thereof fixed to one of the circuit plates and a front surface thereof having primary electrodes; and wiring members electrically connected to the primary electrodes of the semiconductor elements, and wherein in each of the semiconductor units, the multi-layer substrate, the plurality of semiconductor elements, and the wiring members are configured in such a way as to constitute the three-level inverter circuit.