A method of forming a stack-type semiconductor package includes preparing a lower printed circuit board including a plurality of interconnections and a plurality of ball lands for connection on an upper surface thereof. One or more first chips, which are electrically connected to the plurality of interconnections and sequentially stacked, are mounted on the lower printed circuit board. A lower molded resin compound is formed on the lower printed circuit board to cover the first chips, and is formed to have via holes exposing the ball lands for connection. An upper chip package, under which solder balls are formed, is aligned so that the solder balls correspond to the via holes of the lower molded resin compound, respectively. The solder balls are reflown to form connection conductors filling the via holes. A stack-type semiconductor package structure and an electronic system including the same are also provided.