Semiconductor package and fabrication method thereof

A semiconductor package and fabrication method thereof is provided. The semiconductor package comprises a build-up structure, at least one semiconductor element, an encapsulation and a strengthening layer. The build-up structure has opposite a first bottom surface and a first top surface. The semiconductor element is disposed on the first top surface of the build-up structure and electrically connected with the build-up structure. The encapsulation is formed on the first top surface of the build-up structure to cover the semiconductor element. The encapsulation has opposite a second bottom surface and a second top surface, and the second bottom surface faces to the first top surface of the build-up structure. The strengthening layer is formed on the second top surface of the encapsulation, between the build-up structure and the encapsulation, or on the first bottom surface of the build-up structure. Thereby, the invention can reduce situation for warpage of the encapsulation and crack of the semiconductor ele