A system-in-package, comprising a wafer level stack structure, including at least one first device chip including a first device region having a plurality of input/output(I/O) pads, and at least one second device chip including a second device region having a plurality of input/output(I/O) pads and a second peripheral region surrounding the second device region, wherein the size of the second device region is different from the size of the first device region, wherein the at least one first device chip and the at least one second device chip have approximately equal size; and a common circuit board to which the wafer level stack structure is connected.