The MBE growth technique is employed to the intensively studied high K gate dielectrics HFO2 (κ = 20) and its alloy (Hf - Al)O-2 in replacing conventional SiO2 for nano-CMOS applications. Typical 4.9 nm thick HfO2 films showed low leakage current density of ∼ 0.4A/cm(2) at 1 V, a dielectric constant κ of 20.7 and an EOT of 0.9 nm. Minor frequency dispersion is observed at C-V curves and is removed by an improved two-frequency method. An epitaxial order of (1 0 0) cubic HfO2 oxide is observed for the depositions on GaAs(1 0 0) at temperatures over 230° C. © 2005 Elsevier B.V. All rights reserved.