A window-type ball grid array (WBGA) semiconductor package with a lead frame as a chip carrier and a method for fabricating the same are provided. The lead frame has a plurality of leads encompassing an opening, each lead having an upper surface and an opposing lower surface. A resin material is pre-molded on the lower surfaces of the leads, with wire-bonding portions and ball-implanting portions defined on the leads being exposed. At least a chip is mounted on the upper surfaces of the leads and covers the opening, allowing the chip to be electrically connected to the wire-bonding portions of the leads by a plurality of bonding wires via the opening. Then, an encapsulant is formed to encapsulate the chip and fill into the opening for encapsulating the bonding wires. Finally, solder balls are implanted on the ball-implanting portions of the leads to complete fabrication of the semiconductor package.