Ultrathin La2Hf2O7 (LHO) high-k gate dielectric films (similar to 3.4 nm) have been epitaxially grown on Si (0 0 1) substrates through a pulsed laser deposition system. The epitaxial growth characteristics, composition, interface with Si, optical band gap, and electrical properties of the ultrathin LHO films have been investigated by in situ reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS) and transmittance spectroscopy, as well as semiconductor characterization analysis. Results show that ultrathin LHO film grown at 800 degrees C shows a good crystallinity and no obvious interfacial layer forms. La is deficient and oxygen is slightly excessive in LHO film. The epitaxial LHO film has a band gap of similar to 5.7 eV. The gate leakage current density J(g) of the ultrathin epitaxial LHO film follows the space-charge limited conduction mechanism and J(g) is similar to 0.3 A/cm(2) at a gate voltage of 1 V. Additionally, a suitable permittivity similar to 16.7, a small hysteresis similar to 30 mV and a low capacitance equivalent thickness similar to 0.79 nm have been obtained. (C) 2013 Elsevier B.V. All rights reserved.