Silicon containing materials have traditionally been used in microelectronic fabrication. Semiconductor devices often have one or more arrays of patterned interconnect levels that serve to electrically couple the individual circuit elements forming an integrated circuit. These interconnect levels are typically separated by an insulating or dielectric film. Previously, a silicon oxide film was the most commonly used material for such dielectric films having dielectric constants(k) near 4. 0. However, as the feature size is continuously scaling down, the relatively high k of such silicon oxide films became inadequate to provide efficient electrical insulation. As such, there has been an increasing market demand for materials with even lower dielectric constant for Interlayer Dielectric (ILD) applications, yet retaining thermal and mechanical integrity. We wish to report here our investigations on the preparation of ultra-low k ILD materials using a sacrificial approach whereby organic groups are burnt out to generate low k porous ORMOSIL films. We have been able to prepare a variety of organically modified silicone resins leading to highly microporous thin films, exhibiting ultra-low k from 1.80 to 2.87, and good to high modulus, 1.5 to 5.5 Gpa. Structure property influences on porosity, dielectric constant and modulus will be discussed.