A method of forming a wafer level stack structure, including forming a first wafer including a first device chip, wherein the first device chip includes a plurality of input/output (I/O) pads, forming a second wafer including a second device chip, wherein each second device chip contains a second plurality of I/O pads, the second device chip is approximately equal in size to the first chip size, stacking the first wafer and the second wafer, and coupling the first wafer and the second wafer to each other. A method of forming a system-in-package for containing a wafer level stack structure, including forming a wafer level stack structure including a first device chip having a first plurality of input/output (I/O) pads and a second device chip having a second plurality of I/O pads, and forming a common circuit board to which the wafer level stack structure is connected.