A semiconductor package with a heat sink and a method for fabricating the same are proposed. The heat sink is provided with a rigid and thermally resistant detach member on a top surface thereof, and is attached via its bottom surface to a chip mounted on a chip carrier. The detach member is sized larger than the heat sink and can be easily removed from the top surface of the heat sink. Subsequently, a molding process is performed to form an encapsulant for completely encapsulating the chip, the heat sink and the detach member. Then, a singulation process is performed to cut along predetermined cutting lines located between sides of the heat sink and corresponding sides of the detach member. Finally, the detach member and a portion of the encapsulant formed on the detach member are removed from the heat sink. The above fabrication method reduces the packaging cost.