PURPOSE: To absorb thermal stress by providing a movable heat transfer structure having a combination of heat radiators movable in three axial directions perpendicular to each other.

CONSTITUTION: One side faces of one side face microfins 3 are brazed to a back surface of a semiconductor pellet 4, and one fin part of both-side face microfins 2 is engaged with a fin part of an opposite side face. On the other hand, one side faces of one side microfins 1 are also brazed to a bottom of a liquid-cooled jacket 7 to be heat exchanged, and opposite side fin parts of the fins 1 are engaged with the other fin parts of the fins 2. Accordingly, an engaging direction of the fins 3 with the fins 2 is perpendicularly set to that of the fins 1 with the fins 2 thereby to absorb a thermal stress, etc.