Dielectric layers for metal lines in semiconductor chips

A semiconductor structure fabrication method, comprising:

• providing a semiconductor structure which includes:
• (a) a substrate,
• (b) a first device and a second device each being on the substrate,
• (c) a device cap dielectric layer on top of the first and second devices and on top of the substrate, wherein the device cap dielectric layer comprises a device cap dielectric material,
• (d) a first dielectric layer on top of the device cap dielectric layer, wherein the first dielectric layer comprises a first dielectric material, and
• (e) a second dielectric layer on top of the first dielectric layer, wherein the second dielectric layer comprises a second dielectric material;
• and
• forming a first electrically conductive line and a second electrically conductive line each residing in the first and second dielectric layers,
• wherein the first dielectric layer physically separates the first and second electrically conductive lines from the device cap dielectric layer such that both the first and second electrically conductive lines are not in direct physical contact with the device cap dielectric layer, and
• wherein a dielectric constant of the first dielectric material is less than a dielectric constant of the device cap dielectric material.