A fabrication method of a chip scale package includes providing electronic components, each having an active surface with electrode pads and an opposite inactive surface, and a hard board with a soft layer disposed thereon; adhering the electronic components to the soft layer via the inactive surfaces thereof; pressing the electronic components such that the soft layer encapsulates the electronic components while exposing the active surfaces thereof; forming a dielectric layer on the active surfaces of the electronic components and the soft layer; and forming a first wiring layer on the dielectric layer and electrically connected to the electrode pads, thereby solving the conventional problems caused by directly attaching a chip on an adhesive film, such as film-softening, encapsulant overflow, warpage, chip deviation and contamination that lead to poor electrical connection between the electrode pads and the wiring layer formed in a subsequent RDL process and even waste product.