A package structure includes a plurality of first dies, and a plurality of second dies. The plurality of first dies is on first regions of a semiconductor substrate. The plurality of second dies are electrically bonded to the plurality of first dies. The plurality of second dies covers second regions of the semiconductor substrate between the first regions of the semiconductor substrate. The first portion of top surfaces of the plurality of first dies are covered by the plurality of second dies, and the second portions of the top surfaces of the plurality of first dies are exposed by the plurality of second dies.