A semiconductor package includes a core layer having a first surface and a second surface opposite to the first surface. The core layer includes a cavity. A first die is in the cavity. A first gap is between a sidewall of the cavity and a sidewall of the first die. A filling material is in the first gap. The filling material includes a first dimple in proximal to the second surface of the core layer. A first buffer layer on the second surface of the core layer. The first buffer layer has a bottom surface in proximal to the first die and a top surface opposite to the bottom surface. The first buffer layer filling the first dimple. A method for manufacturing a semiconductor package is also disclosed.