The present disclosure relates to methods and apparatus for forming thin-form-factor reconstituted substrates and semiconductor device packages for radio frequency applications. The substrate and package structures described herein may be utilized in high-density 2D and 3D integrated devices for 4G, 5G, 6G, and other wireless network systems. In one embodiment, a silicon substrate is structured by laser ablation to include cavities for placement of semiconductor dies and vias for deposition of conductive interconnections. Additionally, one or more cavities are structured to be filled or occupied with a flowable dielectric material. Integration of one or more radio frequency components adjacent the dielectric-filled cavities enables improved performance of the radio frequency elements with reduced signal loss caused by the silicon substrate.