A method includes forming a redistribution structure on a carrier, attaching an integrated passive device on a first side of the redistribution structure, attaching an interconnect structure to the first side of the redistribution structure, the integrated passive device interposed between the redistribution structure and the interconnect structure, depositing an underfill material between the interconnect structure and the redistribution structure, and attaching a semiconductor device on a second side of the redistribution structure that is opposite the first side of the redistribution structure.