Package structures are provided. A package structure includes an adhesive layer and a semiconductor substrate over the adhesive layer. The package structure also includes a connector over the semiconductor substrate. The package structure further includes a first buffer layer surrounding the connector and the semiconductor substrate and covering the adhesive layer. An interface between the adhesive layer and the first buffer layer is substantially level with a bottom surface of the semiconductor substrate. In addition, the package structure includes an encapsulation layer surrounding the first buffer layer. The package structure also includes a redistribution layer over the first buffer layer and the encapsulation layer.