A semiconductor package including an improved isolation bonding film and methods of forming the same are disclosed. In an embodiment, a semiconductor device includes a first die bonded to a package substrate, the first die including vias extending through a substrate, the vias extending above a top surface of the substrate; a first dielectric film extending along a top surface of the package substrate, along the top surface of the substrate, and along sidewalls of the first die, the vias extending through the first dielectric film; a second die bonded to the first dielectric film and the vias; and an encapsulant over the package substrate, the first die, the first dielectric film, and the second die.