Pb(Zr, Ti)O3 (PZT) thin films with (100) preferred orientation were prepared using metalorganic chemical vapor deposition on LaNiO3 (LNO) buffered platinized Si with thickness varying from 25-100 nm. The dependence of electrical properties of PZT films on thickness was studied using several techniques, including polarization-electric field (P-E), temperature variable current-voltage (I-V), and capacitance-voltage (C-V) measurements. Because of the formation of Schottky barriers at ferroelectric/electrode interfaces, built-in electric fields are present. A progressive increment in carrier concentration and interfacial built-in electric field versus reducing PZT film thickness was observed, which is believed to be a dominant factor controlling the measured dielectric/ferroelectric properties. The higher built-in electric field in thinner PZT films would pin the dipoles at the interfacial region and retard the response of dipoles to the external electric field.