A semiconductor assembly for use with forced liquid and gas cooling. A relatively rigid nano-structure (for example, array of elongated nanowires) extends from an interior surface of a cap toward a top surface of a semiconductor chip, but, because of the rigidness and structural integrity of the nano-structure built into the cap, and of the cap itself, the nano-structure is reliably spaced apart from the top surface of the chip, which helps allow for appropriate cooling fluid flows. The cap piece and nano-structures built into the cap may be made of silicon or silicon compounds.