The etching mechanism of Pb(Zr, Ti) O-3 (PZT) thin films in Cl-2/Ar plasma was investigated through the analysis of gas mixing ratio on volume and surface chemistries. Experiments showed that PZT etch rate keeps a constant value up to 40% of Ar addition into Cl-2/Ar plasma. Langmuir probe measurement showed the noticeable influence of Cl-2/Ar mixing ratio on electron temperature and electron density. The modeling of volume kinetics for neutral and charged particles indicated monotonic changes of both densities and fluxes of active species such as chlorine atoms and positive ions. The analysis of surface kinetics showed that PZT etch rate behavior may be explained by the combination of spontaneous and ion-assisted etch mechanisms.