The present invention relates to a semiconductor device and a manufacturing method thereof. The semiconductor device has a plurality of power units placed in parallel in a predetermined direction, wherein each of the power units includes a plurality of semiconductor elements placed on a metal plate having predetermined gaps with each other. The semiconductor elements of each of the two power units include a near-sided semiconductor element that is closer to an inlet of the resin among the two semiconductor elements having the predetermined gap therebetween. A structure is positioned on a passage and downstream in a resin flow direction relative to a predetermined position that corresponds to end parts of the near-sided semiconductor elements. The structure is a joint to connect the two power units placed adjacent to each other in the predetermined direction, and to be integrally sealed with the resin, along with the power unit.