A method for forming a tantalum-containing gate electrode structure by providing a substrate having a high-k dielectric layer thereon in a process chamber and forming a tantalum-containing layer on the high-k dielectric layer in a thermal chemical vapor deposition process by exposing the substrate to a process gas containing TAIMATA (Ta(N(CH3)2)3(NC(C2H5)(CH3)2)) precursor gas. In one embodiment of the invention, the tantalum-containing layer can include a TaSiN layer formed from a process gas containing TAIMATA precursor gas, a silicon containing gas, and optionally a nitrogen-containing gas. In another embodiment of the invention, a TaN layer is formed on the TaSiN layer. The TaN layer can be formed from a process gas containing TAIMATA precursor gas and optionally a nitrogen-containing gas. A computer readable medium executable by a processor to cause a processing system to perform the method and a processing system for forming a tantalum-containing gate electrode structure are also provided.