Disclosed is a semiconductor package comprising a logic die mounted on an interposer substrate, and a memory stack structure disposed side-by-side with the logic die. The memory stack structure includes a buffer die mounted on the interposer substrate, and a plurality of memory dies stacked on the buffer die. The buffer die has a first surface that faces the interposer substrate and a second surface that faces the plurality of memory dies. The number of data terminals on the second surface is greater the number of connection terminals on the first surface.