The author first applied a chemical mechanical polishing (CMP) process to fabricate a ferroelectric Pb(Zr,Ti)O3 (PZT) capacitor instead of using a plasma etching process for the vertical profile without plasma damage in their previous study. The post-CMP cleaning process was very important in this CMP process. In this study, they investigated the effects of the post-CMP cleaning process on the ferroelectric properties of a PZT thin film capacitor. They proposed an optimized post-CMP cleaning process that uses a SC-1 chemical, diluted HF treatment, and an ultrasonic cleaning process. The slurry residues on the surface of the PZT thin films were removed. The polarization-voltage (P-V) characteristics showed the typical hysteresis loop of PZT thin films after a post-CMP cleaning process with the optimized conditions, while the ferroelectric characteristics could not be observed in the specimen without the post-CMP cleaning process. The remanent polarization (Pr) and coercive voltage (Vc) of the PZT thin films after the post-CMP process with the optimized condition were 17.092 μC/cm2 and 3.252 V, respectively.