US Patent 9349713 Semiconductor package stack structure having interposer substrate

Provided is a semiconductor package stack structure. The semiconductor package stack structure includes a lower semiconductor package, an interposer substrate disposed on the lower semiconductor package and having a horizontal width greater than a horizontal width of the lower semiconductor package, an upper semiconductor package disposed on the interposer substrate, and underfill portions filling a space between the lower semiconductor package and the interposer substrate and surround side surfaces of the lower semiconductor package.