The thermal and dielectric properties of hydrogen methyl silsesquioxane (HMSQ) films thermally treated in nitrogen and in air were investigated quantitatively. The curing processes for both types of HMSQ films included an exothermic process accompanying weight loss and the structure transformed from cage into network structure. A higher percentage of the weight loss and higher degree of conversion were achieved for air cured films. The dielectric constants were about 2.64 and 2.71 for nitrogen and air cured films, respectively. The leakage current density was on the order of 10(-8) A/cm(2) at 1 MV/cm for both types of films. (C) 2003 Elsevier B.V. All rights reserved.