Abstract: A heat sink adapted for dissipating heat from a semiconductor device. The heat sink has lower heat sink body, an upper heat sink body soldered to the lower heat sink body, an airtight chamber defined in between the upper heat sink body and the lower heat sink body and drawn into a vacuum status, a working fluid filled in the airtight chamber for circulation between gas phase and liquid phase to transfer heat energy from the bottom side of the heat sink toward the top side thereof, and a porous structure formed in the upper heat sink body and the lower heat sink body inside the airtight chamber for accelerating the circulation of the working fluid between gas phase and liquid phase.