Patent ID: 7041574

Claim:
A method of forming a composite intermetal dielectric structure, comprising: providing an initial intermetal dielectric structure comprising a first dielectric layer and two conducting lines, wherein the two conducting lines are located in the first dielectric layer; forming a nonconductive patterned trench mask over the initial intermetal dielectric structure; removing a portion of the first dielectric layer between the conducting lines to form a trench in alignment with the trench mask; filling the trench with a second dielectric material, wherein the second dielectric material is a substantially solid material, wherein the second dielectric material is a low-k dielectric having a dielectric constant less than that of the first dielectric layer; etching the second dielectric material so that it is recessed relative to the conducting lines; forming a cap layer over the second dielectric material; and planarizing the cap layer to be substantially coplanar with the conducting lines.