We introduced a high porosity ultralow-k film into a Cu damascene interconnect without increasing the dielectric constant (k) of a low-k film after interconnect formation. A high elastic modulus (9 GPa) with ultralow-k value (< 2.1) was achieved by using a self-assembled porous silica film formed with UV irradiation and a silylation anneal. Performing the silylation anneal after trench etching results in recovery of the k value and dielectric properties. A sidewall protection process carried out before metalization protects the low-k film against process-induced damage. The time-dependent-dielectric breakdown lifetime is 10 years at a high electric field of 2.3 MV/cm.