TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: At least one of the first source compounds is nitrogen gas, hydrogen gas and/or noble gas, or the second source compound is silane and/or disilane.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The process chamber further comprises: a blocker plate disposed between the metal filament assembly and the first showerhead assembly, and the first source inlet; and a second showerhead assembly disposed between the metal filament assembly and the first source inlet. The second showerhead assembly comprises a face plate consisting of a single-zone face plate, and/or a dual-zone face plate. The metal filament assembly is connected to a power supply to deliver an electrical current through the metal filaments and form the radicals of the first source compound inside the process chamber. The first channels are formed through an upper surface and a lower surface of the dual-zone face plate to deliver the first source compound in fluids, gases and/or radicals into the substrate processing zone. The second channels are formed on the lower surface of the dual-zone face plate facing the substrate processing zone, and are connected to the fluid conduit of the showerhead body to deliver the second source compound into the substrate processing zone without passing the second source compound through the metal filament assembly or forming any plasma. The diameters of the first channels are larger than diameters of the second channels. Each first channel is disposed between two or more second channels on a lower surface of the dual-zone face plate of the showerhead assembly and configured to enhance the chance of reaction of the radicals of the first source compound with the second source compound. The fluid conduit of the showerhead body is connected to a second source inlet to deliver the second source compound into the process chamber. The showerhead assembly further comprises at least one of: one or more cooling channels; or one or more heating elements or heating channels. The dual-zone face plate of the showerhead assembly is formed by welding a top plate and a bottom plate together with a plenum between the plates. The plenum is connected to the fluid conduit and the second channels for delivering the second source compound. The first channels are formed to pass through the top plate, the plenum, and the bottom plate without contacting the second channels or the plenum between the top plate and the bottom plate, where the second channels are formed from the plenum through the bottom plate. Preferred Method: The method further comprises delivering the first source compound through a second showerhead assembly prior to flow of the first source compound through the metal filaments. A thin film is formed over the surface of the substrate at a temperature, which is lower than 1000 degrees C of a thermal chemical vapor deposition (CVD) process, without use of a plasma and from a mixture of the second source compound and the radicals of the first source compound.