Thin films of dielectric materials are used as insulating layers in microelectronic systems, including integrated circuits and printed circuit boards. Polymer and spin-on-glasses are widely used as coatings and interlevel dielectrics. The dielectric permitivity and loss are the electrical properties of most interest. However, characterization and optimization of the mechanical properties is essential to the successful implementation and usage of these insulators. In this presentation, thin-film structures for measuring direction-dependent properties (dielectric constant, elastic modulus, and coefficient of thermal expansion), and nano-indentation results on spin-on-glass materials will be presented. Significant improvement in the fracture toughness of nanoporous methylsilsesquioxane glass films has been demonstrated upon introduction of porosity into the films.