New hafnium β-diketonato-silylamide and siloxides namely Hf(thd) 2 [N(SiMe 3 ) 2 ] 2 (1), Hf(thd) 2 (OSiMe 3 ) 2 (2) and Hf(thd) 2 (OSi t BuMe 2 ) 2 (3) (thd=2,2,6,6-tetramethyl-3,5-heptanedionate) were investigated as single-source precursors for low-pressure pulsed liquid injection MOCVD of HfSi x O y thin films on Si(100) and R-plane sapphire. Films were characterized by XRD, XPS and AFM. The growth rate increased in order 1>2>3 in agreement with the decreasing precursor thermal stability. The activation energy was ∼80–100kJ/mol. The as-deposited at 550–800°C films were essentially amorphous; hafnia reflections appeared after 1h annealing at 900°C probably due to phase separation into amorphous Si-rich silicate and crystallized HfO 2 . The surface of the films showed similar amounts of Hf and Si (∼1:1) and was overstoichiometric in oxygen (ratio O/(Hf+Si) >2). The bulk of the films was Hf-rich (70–85% of Hf/ Hf+Si) and slightly oxygen-deficient. The new complexes are attractive single-source precursors for the deposition of pure and very smooth (R a ∼0.7nm, <1% relative to thickness) HfSi x O y films. Dielectric constant 11.3 and leakage current density 8×10 −4 A/cm 2 (at −1V) were measured for a 22nm thick film.