Manufacturing method of semiconductor device and semiconductor device

A semiconductor device includes a die pad, which includes an upper surface and a lower surface opposite to the upper surface, the upper surface forming a rectangular shape in plain view; a plurality of support pins that support the die pad; a plurality of inner leads arranged around the die pad; a plurality of outer leads connected to each of the inner leads; a semiconductor chip which includes a main surface and a back surface opposite to the main surface and in which a plurality of electrode pads is formed in the main surface. The die pad includes a first side, a second side opposite to the first side, and a third side and a fourth side, which intersect the first and second sides.