The present invention provides a composition for preparing porous dielectric thin films containing pore-generating material, said composition comprising gemini detergent, and/or a quaternary alkyl ammonium salt, a thermo-stable organic or inorganic matrix precursor, and solvent for dissolving the two solid components. There is also provided an interlayer insulating film having good mechanical properties such as hardness, modulus and hydroscopicity, which is required for semiconductor devices.