A package structure includes a first die, at least one second die, a semiconductor substrate and a glue layer. The semiconductor substrate includes no active devices. The glue layer is disposed between the at least one second die and the semiconductor substrate. The glue layer has a top surface adhered to the least one second die and a bottom surface adhered to a topmost surface of the semiconductor substrate. A total area of the bottom surface of the glue layer is substantially equal to a total area of the topmost surface of the semiconductor substrate, and a total thickness of the first die is substantially equal to only a total thickness of the at least one second die, the semiconductor substrate and the glue layer.