A multi-chip module (MCM) integrated circuit package structure is proposed, which can be used to pack a plurality of semiconductor chips of different functions while nonetheless allowing the overall package size to be as small as some existing types of integrated circuit packages, such as the SO (Small Outline) and QFP (Quad Flat Package) types, so that it can be manufactured using the existing fabrication equipment. The proposed MCM integrated circuit package structure is characterized in the use of a substrate having a centrally-located opening, and at least one semiconductor chip is mounted on the front surface of the substrate and a semiconductor chip of a central-pad type having a plurality of centrally-located bonding pads is mounted on the back surface of the substrate with the centrally-located bonding pads being exposed through the opening. This arrangement allows the overall package size to be made very compact and also allows the wiring to the central-pad type semiconductor chip to be shortened.