Ferroelectric lead zirconium titanate (Pb (ZrxTi1-x) O3) thin films with various thicknesses were fabricated on Pt/Ti/SiO2/Si substrates using the sol-gel method with 2.45 GHz microwave energy. Investigations have been made on the crystal structure, surface morphology, dielectric and ferroelectric properties of the films. The thicknesses of PZT film were in the range of 99 to 420 nm, and films were annealed at 450°C for 30 min. The 99 and 168 nm-thick PZT films have mixed pyrochlore and perovskite phases. Above 168 nm-thick PZT films have complete perovskite phase. The full width at half maximum (FWHM), and the surface roughness were decreased as the film thickness increased. Relative dielectric constant and remnant polarization increased as the film thickness increased, which reflect the difference in crystallinity.