One aspect of this disclosure relates to an integrated circuit structure. An integrated circuit structure embodiment includes a substrate, a gate dielectric over the substrate, a carbon structure having a predetermined thickness in contact with and over the gate dielectric, and a layer of desired gate material for a transistor in contact with and over the carbon structure. The layer of desired gate material includes a predetermined thickness corresponding to the predetermined thickness of the carbon structure to support a metal substitution process to replace the carbon structure with the desired gate material. Other aspects and embodiments are provided herein.