A package-on-package semiconductor assembly is characterized by a semiconductor device positioned in a dielectric recess of a core base and surrounded by an array of metal posts. The recess in the core provides lateral displacement control between the device and the metal posts, and the minimal height of the metal posts needed for the vertical connection between two both opposite sides of the core base can be reduced by the amount equal to the depth of the recess. Further, another semiconductor device is disposed over a top surface of the core base and is electrically coupled to the semiconductor device in the dielectric recess through a buildup circuitry under a bottom surface of the core base.