We have employed molecular beam epitaxy (MBE) to grow high kappa dielectric nano-thick films of Al2O3 and HfO2 on Si (100) as templates to suppress effectively the formation of the oxide/Si interfacial layer during the subsequent atomic layer deposition (ALD) growth for Al2O3. We show marked improvements of electrical performance of the ALD + MBE composite oxides. A first bi-layer composite of ALD Al2O3 1.9 nm/MBE Al2O3 1.4 nm showed a dielectric constant of 9.1 with an equivalent oxide thickness (EOT) of 1.41 nm. The interfacial trap density D-it was 2.2 x 10(11) cm(-2) eV(-1) as deduced from the conductance method, with the leakage current density being 2.4 x 10(-2) A/cm(2) at V-fb-1 V. The second bi-layer of ALD Al2O3 3.0 nm/MBE HfO2 2.0 rurt showed a dielectric constant of 11.5 and an EOT of 1.7 nm. The D-it was estimated to be 2 x 10(11) cm(-2) eV(-1) with the leakage being 1.1 x 10(-4)A/cm(2) at V-fb + 1 V. (c) 2007 Elsevier B.V. All rights reserved.