A logic chip and memory chip stacked over the logic chip, the logic chip having a first surface facing the memory chip and a second surface opposite to the first surface and including: first and second internal input/output circuit units for exchanging signals; first external input/output circuit unit for exchanging signals through first external input/output pads formed according to an external interface standard of a first memory over the second surface; and second external input/output circuit unit for exchanging signals through second external input/output pads formed according to an external interface standard of a second memory over the second surface, wherein semiconductor device operates in one of a first mode in which the first internal input/output circuit unit and the first external input/output circuit unit are enabled and a second mode in which the first and second internal input/output circuit units and the second external input/output circuit unit are enabled.