Electrical properties and thermal stability have been studied in molecular beam epitaxy (MBE)-grown high-kappa dielectric Al2O3/HfO2 on Ge substrate. An abrupt HfO2/Ge interface without any interfacial layer was revealed using high-resolution transmission electron microscope and angle-resolved X-ray photoelectron spectroscopy. Capacitance-voltage characteristics, exhibiting accumulation and inversion and a high kappa-value of about 20 for HfO2, and a low leakage current density at flat-band voltage +1 V of 8 X 10(-5) A/cm(2) were obtained for metal-oxide-semiconductor capacitors (MOSCAPs) of Al2O3(3.3 nm)/HfO2(2.8 nm)/Ge annealed at 500 degrees C in N-2 ambient for 20 min. MBE-grown Al2O3/HfO2 is the promising high-kappa dielectric to realize a high-performance Ge metal-oxide-semiconductor field-effect-transistor. (c) 2008 Elsevier B.V. All rights reserved.