Abstract: A ball grid array semiconductor package using a flexible circuit board, in which the flexible circuit board has no conductive via hole nor solder mask while having a thin structure formed at only one surface thereof with a circuit pattern having a small length. The flexible circuit board is mounted with a metallic carrier frame to achieve an easy handling thereof, a reduction in the inductance, impedance and coupling effect of adjacent circuit patterns and an easy discharge of heat from a semiconductor chip, thereby achieving an improvement in electrical performance and an improvement in heat discharge performance. The metallic carrier frame has a plurality of openings adapted to increase the bonding force between an encapsulate and constituting elements of the package, thereby removing a bending phenomenon of the package, and a method for fabricating such a BGA semiconductor package. The invention also provides a method for fabricating such a BGA semiconductor package.