Tuning effective metal gate work function by a novel gate dielectric HfLaO for nMOSFETs

Using a novel HfLaO gate dielectric for nMOSFETs with different La composition, we report for the first time that TaN (or HfN) effective metal gate work function can be tuned from Si mid-gap to the conduction band to fit the requirement of nMOSFETs. This is explained by the change of interface states and Fermi pinning level by adding La into HfO₂. The superior performances of the nMOSFETs compared with those using pure HfO₂ gate dielectric are also reported, in terms of higher crystallization temperature and higher drive current I_d without sacrifice of very low gate leakage current, i.e. 5-6 orders reduction compared with SiO₂ at the same equivalent oxide thickness of ∼1.2-1.8 nm.