Manufacturing a wafer level stack package includes the steps of back-grinding a lower surface of a wafer including a plurality of first semiconductor chips. A support member is attached to a lower surface of the back-grinded wafer. One or more second semiconductor chips are stacked on the respective first semiconductor chips of the back-grinded wafer. First through-electrodes are formed to electrically connect the stacked first semiconductor chips and second semiconductor chips. Third semiconductor chips are attached to uppermost ones of the stacked second semiconductor chips, and the third semiconductor chips have second through-electrodes which are electrically connected to the first through-electrodes and re-distribution lines which are connected to the second through-electrodes. Outside connection terminals are attached to the re-distribution lines of the third semiconductor chips. The first semiconductor chips of a wafer level on which the second and third semiconductor chips are stacked are sawed to for semiconductor packages at a chip level.