Pb(Zr,Ti)O3 (PZT) and Pb(Zr,Ti,Nb)O3 (PNZT) thin films have been grown on platinized silicon substrates by RF magnetron sputtering followed by a post-annealing treatment. The niobium, Nb, concentration varied from 1 to 7 at.% by increment of 1 at.% The effects of the Nb introduction on the PZT electrical properties, i.e., dielectric and ferroelectric ones have been investigated. We have found that the relative dielectric constant $(\varepsilon_{\rm r})$ is very sensitive to the Nb introduction; $(\varepsilon_{\rm r})$ reaches 1100 for a PNZT film doped at 2 at.% in comparison to 820 for a PZT film. The ferroelectric properties are also dependent of the doping level; in particular the remnant polarization reaches its maximum value ($17 \mu$C/cm2) for a 2 at.% Nb doped PZT film.