A semiconductor package with a build-up structure is provided, which includes a rigid base, a rigid frame having a through hole and fixed onto the rigid base, at least one chip received in the through hole of the rigid frame, a medium filled in a gap between the chip and the rigid frame, a build-up structure formed on the chip and the rigid frame and electrically connected to the chip, and a plurality of conductive elements bonded to the build-up structure to electrically connect the chip to external devices. The use of the rigid base and rigid frame can avoid structural warpage, cracking, delamination and a popcorn effect of the semiconductor package. A method for fabricating the semiconductor package is also provided.