1. A method for manufacturing stacked packages by stacking a plurality of semiconductor device packages, said method comprising: preparing lead frames, each lead frame including a chip receiving cavity, a plurality of inner leads having a designated thickness, said inner leads arranged along opposite two sides of the chip receiving cavity, a plurality of connection terminals having a smaller thickness than that of the inner leads, each connection terminal formed on a terminal end of the inner lead, said terminal end lying adjacent to the chip receiving cavity, a plurality of outer leads integrated with the inner leads, dam bars formed perpendicular to the inner and the outer leads in order to partition leads into the inner and the outer leads, tie bars formed on opposite two sides other than the sides on which the inner leads are formed, and a side frame supporting the outer leads, the dam bars, and the tie bars; attaching an adhesive tape to the lower surface of the lead frame; bonding a semiconductor chip to the adhesive tape in the chip receiving cavity between the leads; connecting the semiconductor chip to the connection terminals; forming a package body by encapsulating the semiconductor chip, the inner leads, the connection terminals, and electrical connection parts between the semiconductor chip and the connection terminals, so as to expose the upper surfaces of the inner leads to the package body; removing the adhesive tape; removing dam bars from the side frame; separating packages from the lead frame; and forming a stacked package by stacking a plurality of the packages, wherein each of the packages is stacked on another package by electrically connecting the exposed upper and lower surfaces of the inner leads with each other, and the stacked package is electrically connected to an external printed circuit board by outer leads of a lowermost package.