The invention provides a semiconductor device and associated method, which includes a substrate, a first die, multiple sub-package systems surrounding the first die, and a heat spreader. The first die and the sub-package systems are installed on a same surface of the substrate, wherein projections of the first die and each sub-package system on the surface partially overlap, and have a portion not overlapping. Each of the sub-package systems includes an interposer and multiple second dice installed on the interposer by way of flip-chip. The heat spreader includes a protrusion portion and a dissipation plate; the dissipation plate covers the first die and the sub-package systems, and the protrusion portion is set between the dissipation plate and the first die.