HfO2/HfSixOy high-k gate stack with very low leakage current for low-power poly-Si gated CMOS application

Poly-Si gated NMOSFETs, with HfO₂/HfSi_xO_y gate stacks for CMOS low-power application are reported for the first time. Compared to an SiO₂ control sample, the HfO₂/HfSi_xO_y stack with equivalent oxide thickness of about 18 Å exhibits four-orders of magnitude reduction in gate leakage at V_g=1 V. Additionally, negligible hysteresis and comparable subthreshold swing are observed, indicating good interface quality and bulk film properties. Furthermore, the stack-caused inherent transconductance degradation is small; almost 66% of the normalised peak transconductance with respect to SiO₂ can be reached.