Ferroelectric $Pb(Zr,Ti)O_3$ thin films were prepared on the Pt coated Si substrates at 450℃~490℃ by the electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) method. Bisdipivaloylmethanato lead [$Pb(DPM)_2$], Zirconium tert-butoxide [$Zr(O-t-C_4H_9)_4$], titanium iso-propoxide [$Ti(O-i-C_3H_7)_4$] were used as Pb, Zr and Ti source materials, respectively. The compositional ratio Zr/Ti in the PZT films was propotional to the ratio of Zr and Ti MO source flow rates. At the early stage of the PZT deposition, pyroclore phase interfatial layer was formed on which perovskite grains grow. The interfacial layer disappeared as the deposition process continued. After the rapid thermal annealing process at 650℃ for 1 minute, a typical 50nm thick PZT film had relative dielectric constant of about 1200 and $SiO_2$ equivalent thickness of about 0.14nm. The role of interfacial layer was discussed and related to the properties of the PZT films.