A method of forming a package structure includes disposing a semiconductor device over a first dielectric layer, wherein a first redistribution line is in the first dielectric layer, forming a molding compound over the first dielectric layer and in contact with a sidewall of the semiconductor device, forming a second dielectric layer over the molding compound and the semiconductor device, forming a first opening in the second dielectric layer, the molding compound, and the first dielectric layer to expose the first redistribution line, and forming a first conductor in the first opening, wherein the first conductor is electrically connected to the first redistribution line.