A semiconductor assembly includes a semiconductor device, a heat spreader, an adhesive and a build-up circuitry. The heat spreader includes a bump, a base and a flange. The bump defines a cavity. The semiconductor device is mounted on the bump at the cavity, electrically connected to the build-up circuitry and thermally connected to the bump. The bump extends from the base into an opening in the adhesive, the base extends vertically from the bump opposite the cavity and the flange extends laterally from the bump at the cavity entrance. The build-up circuitry includes a dielectric layer and conductive traces on the semiconductor device and the flange. The conductive traces provide signal routing for the semiconductor device.