A semiconductor device includes: a dielectric substrate; an integrated circuit (IC) die disposed inside an opening of the dielectric substrate, where the IC die is configured to transmit or receive radio frequency (RF) signals; a dielectric material in the opening of the dielectric substrate and around the IC die; a redistribution structure along a first side of the dielectric substrate, where a first conductive feature of the redistribution structure is electrically coupled to the IC die; a second conductive feature along a second side of the dielectric substrate opposing the first side; a via extending through the dielectric substrate, where the via electrically couples the first conductive feature and the second conductive feature; and an antenna at the second side of the dielectric substrate, where the second conductive feature is electrically or electromagnetically coupled to the antenna.