Abstract: Using hydrofluoric acid as acid catalyst, F doped nanoporous low-k SiO2 thin films were prepared through sol-gel method. Compared with the hydrochloric acid catalyzed film, the films showed better micro structural and electrical properties. The capacitance-voltage and current-voltage characteristics of F doped SiO2 thin films were then studied based on the structures of metal-SiO2-semiconductor and metal-SiO2-metal, respectively. The density of state (DOS) of samples deposited on metal is found to decrease to a level of 2 × 1017 eV−1 cm−3. The values of mobile ions, fix positive charges, trapped charges and the interface state density between the SiO2/Si interfaces also decrease obviously, together with the reduction of the leakage current density and the dielectric constant, which imply the improvement of the electrical properties of thin films. After annealing at a temperature of 450∘C, the lower values of the leakage current density and dielectric constant could be obtained, i.e. 1.06 × 10−9 A/cm2 and 1.5, respectively.