In the study, the film properties and chemical mechanical polishing (CMP) characteristics of the low‐dielectric‐constant materials hydrogen silsesquioxane (HSQ) and methyl silsesquioxane (MSQ) were presented. The Fourier transform infrared spectra, refractive index, dielectric constant, and atomic force microscopy results showed the successful preparation of the HSQ and MSQ films. The CMP characteristics of both materials were studied by two different ZrO2‐normalbased slurries, A‐1 and B‐1. Our results showed that the CMP removal rate and nonuniformity increased with increasing the slurry solid content. The removal rate of the polished HSQ film was much larger than that of the polished MSQ film due to the hydrophobic surface of the MSQ film. The removal rate using the A‐1 slurry was larger than the B‐1 slurry for polishing both films. This result can be explained from the consideration of the isoelectric point and the electrostatic force between the abrasive surface and the film surface. The downforce pressure of the CMP process also showed a significant effect on the removal rate and the nonuniformity of the polished HSQ film. © 1999 The Electrochemical Society. All rights reserved.