Abstract: A first substrate includes a first surface and a second surface opposite to the first surface. A second substrate includes a third surface and a fourth surface opposite to the third surface. A third substrate includes a fifth surface and a sixth surface opposite to the fifth surface. The first substrate is made of an insulator, and includes a mounting portion for mounting an electronic element at the first surface, and the mounting portion is a rectangular shape. The third substrate is made of a carbon material, and the fifth surface is connected to at least the second surface at location overlapped with the mounting portion in plan view. The third substrate has a larger heat conduction in a direction perpendicular to the longitudinal direction of the mounting portion than heat conduction in the longitudinal direction of the mounting portion in plan view.

Abstract: Various embodiments provide semiconductor devices having cavity substrate structures for package-on-package assembly and methods for their fabrication. In one embodiment, the cavity substrate structure can include at least one top interconnect via formed within a top substrate. The top substrate can be disposed over a base substrate having at least one base interconnect via that is not aligned with the top interconnect via. Semiconductor dies can be assembled in an open cavity of the top substrate and attached to a base center portion of the base substrate of the cavity substrate structure. A top semiconductor package can be mounted over the top substrate of the cavity substrate structure.