Thin LaxZr1−xO2−δ (x=0.25) high permittivity (k) films are grown on Si(100) by atomic layer deposition at 300 °C using (PirCp)3La, (MeCp)2ZrMe(OMe) and O3 species. Their properties are studied by grazing incidence x-ray diffraction, high resolution transmission electron microscopy, electron energy loss spectroscopy, x-ray photoelectron spectroscopy, and electrical measurements on the as-grown films and after vacuum annealing at 600 °C. Annealed films feature resistance to hygroscopicity, a large k value of around 30 and an acceptable leakage current density. A low-k silica-rich interlayer is also evidenced at both pristine and annealed high-k/Si interfaces.