Abstract: A lead-frame-based semiconductor package and a fabrication method thereof are proposed. The semiconductor package includes: a lead frame having a plurality of first and second leads, wherein each first lead is formed with an extending portion smaller in thickness than the first lead in a manner that, an upper surface of the extending portion is flush with an upper surface of the first lead, and a lower surface of the extending portion forms a height difference with respect to a lower surface of the first lead; a chip mounted over the upper surfaces of the extending portions, and electrically connected to the leads by bonding wires; an encapsulant for encapsulating the upper surfaces of leads, upper surfaces of extending portions, chip and bonding wires; and a non-conductive material applied over the lower surfaces of extending portions, wherein the lower surfaces of leads are exposed to outside of the non-conductive material.