A semiconductor package includes an encapsulated semiconductor device, a redistribution structure, and a protection layer. The encapsulated semiconductor device includes a semiconductor device and an encapsulating material encapsulating the semiconductor device. The redistribution structure is disposed on the encapsulated semiconductor device and includes a dielectric layer and a redistribution circuit layer electrically connected to the semiconductor device. The protection layer at least covers the dielectric layer, wherein an oxygen permeability or a water vapor permeability of the protection layer is substantially lower than an oxygen permeability or a vapor permeability of the dielectric layer.