A package includes a first device die, and a first encapsulating material encapsulating the first device die therein. A bottom surface of the first device die is coplanar with a bottom surface of the first encapsulating material. First dielectric layers are underlying the first device die. First redistribution lines are in the first dielectric layers and electrically coupling to the first device die. Second dielectric layers are overlying the first device die. Second redistribution lines are in the second dielectric layers and electrically coupling to the first redistribution lines. A second device die is overlying and electrically coupling to the second redistribution lines. No solder region connects the second device die to the second redistribution lines. A second encapsulating material encapsulates the second device die therein. A third device die is electrically coupled to the second redistribution lines. A third encapsulating material encapsulates the third device die therein.