PURPOSE: To reduce thermal resistance over a region from a junction of a semiconductor chip to a cooling fluid.

CONSTITUTION: A semiconductor chip 1 is mounted on a principal surface of a wiring board 2 through a solder bump 3. A top 4 is bonded through a solder 7 with the rear surface of the semiconductor chip 1 where the solder bump 3 is not existent. A groove 15 is provided in the top 4, and a flow passage 6 is constructed between the top 4 and the back of the semiconductor chip 1. A microconnector 5 communicated with a start end 22 or a final end 23 of the flow passage 6 is mounted on the top 4. A cooling fluid 21 is fed from the microconnector 5 to the start end 22 and is discharged from the microconnector 5 to the final end 22. The back surface of the semiconductor chip 1 is directly cooled with the cooling fluid 21 so that thermal resistance is sharply reduced.