The disclosure provides a method of forming a package structure, and the method includes the following steps. A plurality of semiconductor components is bonded to a substrate. A grinding process is performed to thin the plurality of semiconductor components. The plurality of semiconductor components have a first total thickness variation (TTV) after performing the grinding process. A dielectric layer is formed on the substrate. A first chemical mechanical polishing (CMP) is performed to remove a first portion of the dielectric layer on top surfaces of the plurality of semiconductor components; and performing a second CMP process to remove a second portion of the dielectric layer between the plurality of semiconductor components and a portion of the plurality of semiconductor components. After performing the second CMP process, the plurality of semiconductor components has a second TTV less than the first TTV.