An electronic device includes an embedded die frame having a cavity and a routing structure, a semiconductor die in the cavity with a gallium nitride layer on the routing structure, and a heat spreader having a thermally conductive insulator layer and a metal plate, the thermally conductive insulator layer having a first side that faces the embedded die frame and an opposite second side that faces away from the embedded die frame, with a portion of the first side of the thermally conductive insulator layer extending over a side of a silicon substrate of the semiconductor die, and the metal plate on the second side of the thermally conductive insulator layer.