The silsesquioxane (SSQ) films with low dielectric constant have been successfully synthesized by covalently binding a thermally decomposable porogen [poly(amidoamine), PAMAM] to a host polymer (hydrogen methyl silsesquioxane, HMSQ) via a coupling agent. The decomposition behavior of the porogen as well as the thermal and dielectric properties of the host polymer heat-treated in different atmospheres have been studied and compared. The dielectric properties of the HMSQ-PAMAM porous films have been investigated as a function of porogen concentration. An average dielectric constant about 2.06 could be obtained with leakage current density on the order of 10(-7) A/cm(2) for a film with 20-wt.% loading of the PAMAM polymer. (C) 2004 Elsevier B.V. All rights reserved.