Bumpless build-up layer (BBUL) semiconductor packages with ultra-thin dielectric layers are described. For example, an apparatus includes a semiconductor die including an integrated circuit having a plurality of external conductive bumps. A semiconductor package houses the semiconductor die. The semiconductor package includes a dielectric layer disposed above the plurality of external conductive bumps. A conductive via is disposed in the dielectric layer and coupled to one of the plurality of conductive bumps. A conductive line is disposed on the dielectric layer and coupled to the conductive via.