The physical and electrical characteristics of high-kappa gate dielectric Hf(1-x)LaxOy were systematically investigated in this work. Cross-sectional transmission electron microscopy and X-ray diffraction confirmed that HfO2 film crystallized after annealing at 900 degrees C for 30 s. On the other hand, Hf(1-x)LaxOy films with x = 0.15 (15% La) and x = 0.5 (50% La) remained amorphous even after annealing at 900 degrees C for 30 s. Moreover, NMOSFETs fabricated with Hf(1-x)LaxOy films exhibit superior electrical performances in terms of drive current, electron mobility, charge trapping induced threshold voltage instability and gate leakage current compared to NMOSFETs fabricated with HfO2 films. We also report for the first time the effective workfunction tuning of TaN (or HfN) metal gate with the incorporation of La to meet the workfunction requirements of NMOSFETs. These unique and advantageous characteristics of Hf(1-x)LaxOy make it a promising high-kappa gate dielectric to replace SiO2 and SiON to meet the international technology roadmap for semiconductors (ITRS) requirements for high-kappa dielectrics. (c) 2006 Elsevier Ltd. All rights reserved.