SEMICONDUCTOR DEVICE

A cooling case has outer lateral surfaces located on long sides and outer lateral surfaces located on short sides thereof in plan view. The cooling case has a flow passage having a concave shape therein. The flow passage includes a main passage, and an inflow passage recessed from a bottom surface of the main passage toward a bottom side of the cooling case. The cooling case further has an inlet that is provided at one of the outer lateral surface to be directly connected to the inflow passage. The inlet introduces a cooling medium that flows through the inlet in a longitudinal direction of the cooling case toward the flow passage and the inflow passage has a diffusion surface that faces an opening of the inlet.