Disclosed are semiconductor packages and their fabrication methods. The semiconductor package comprises providing a semiconductor substrate, forming a semiconductor element on an active surface of the semiconductor substrate, forming in the semiconductor substrate through vias that extend from the active surface into the semiconductor substrate, forming a first pad layer on the active surface of the semiconductor substrate, performing a first planarization process on the first pad layer, performing on an inactive surface of the semiconductor substrate a thinning process to expose the through vias, forming a second pad layer on the inactive surface of the semiconductor substrate, performing a second planarization process on the second pad layer, and after the second planarization process, performing a third planarization process on the first pad layer.