The present disclosure relates to a radio frequency (RF) device that includes a mold device die and a multilayer redistribution structure underneath the mold device die. The mold device die includes a device region with a back-end-of-line (BEOL) portion and a front-end-of-line (FEOL) portion over the BEOL portion, a thermally conductive film, and a first mold compound. The FEOL portion includes isolation sections and an active layer surrounded by the isolation sections. The thermally conductive film, which has a thermal conductivity greater than 10 W/m·K and an electrical resistivity greater than 1E5 Ohm-cm, resides between the active layer and the first mold compound. Herein, silicon crystal does not exist between the first mold compound and the active layer. The multilayer redistribution structure includes a number of bump structures, which are at a bottom of the multilayer redistribution structure and electrically coupled to the FEOL portion of the mold device die.