A method for fabricating a semiconductor die involves providing a semiconductor substrate, forming a plurality of active devices and a plurality of passive devices over the semiconductor substrate, forming one or more electrical connections to the plurality of active devices and the plurality of passive devices, forming one or more dielectric layers over at least a portion of the electrical connections, applying an interface material over at least a portion of the one or more dielectric layers, removing portions of the interface material to form a plurality of trenches, and covering at least a portion of the interface material and the plurality of trenches with a substrate layer to form a plurality of radio-frequency isolation cavities.