Controlling work function and damaging effects of sputtered RuO₂ gate electrodes by changing oxygen gas ratio during sputtering.

RuO₂ metal gates were fabricated by a reactive sputtering method under different O₂ gas ratios. For the given sputtering power of 60 W, a ∼13% O₂ ratio was the critical level below or over which RuO₂ film has hyperstoichiometric and stoichiometric compositions, which resulted in a difference in the effective work function by ∼0.2 eV. The stoichiometric RuO₂ film imposes almost no damaging effect to the underlying SiO₂ and HfO₂ gate dielectrics. The RuO₂ gate decreased the equivalent oxide thickness by ∼0.5 nm and leakage current by around two orders of magnitude compared to the Pt-gated samples.