A method includes performing a first molding process to enclose a portion of a first semiconductor die in a first package structure with an opening that exposes a portion of a second semiconductor die mounted to the first semiconductor die, as well as performing a deposition process to deposit a stress absorbing material in the opening of the first package structure to cover the portion of the second semiconductor die, and performing a second molding process to enclose a portion of the stress absorbing structure in a second package structure that extends on a side of the first package structure.