A semiconductor package on which a semiconductor device can be stacked and fabrication method thereof are provided. The fabrication method includes the steps of mounting and electrically connecting at least one semiconductor chip on the substrate, mounting an electrical connecting structure consisting of an upper layer circuit board and a lower layer circuit board on the substrate and electrically connecting the electrical connecting structure to the substrate, where the semiconductor chip is received in a receiving space formed in the electrical connecting structure; forming an encapsulant on the substrate encapsulating the semiconductor chip and the electrical connecting structure, and after the encapsulant is formed, exposing top surface of the upper layer circuit board with a plurality of solder pads from the encapsulant to allow at least one semiconductor device to electrically connect the upper layer circuit board so as to form a stack structure.