One aspect of this disclosure relates to a method for forming a transistor. According to various method embodiments, a gate dielectric is formed on a substrate, a substitutable structure is formed on the gate dielectric, and source/drain regions for the transistor are formed. A desired gate material is substituted for the substitutable structure to provide the desired gate material on the gate dielectric. Some embodiments use carbon for the substitutable material, and some embodiments use silicon, germanium or silicon-germanium for the substitutable material. Some embodiments form a high-k gate dielectric, such as may be formed by an atomic layer deposition process, an evaporated deposition process, and a metal oxidation process. Other aspects and embodiments are provided herein.