Interconnect Structure Having Air Gap and Method of Forming the Same

A semiconductor device, comprising:

• first and second openings in a first dielectric layer overlying a substrate;
• a conformal dense layer on sidewalls of the first and second openings;
• a barrier layer at a bottom surface and sidewalls of the first and second openings;
• first and second conductive features in first and second openings, respectively;
• a third opening in the first dielectric layer between the first and second conductive features, wherein the third opening exposes the conformal dense layer between the first and second conductive features;
• and
• a second dielectric layer having an air gap between the first and second conductive features.

A semiconductor device, comprising:

• a first dielectric layer having a first and second trench therein;
• a dielectric liner lining the first trench and the second trench, the dielectric liner having a dielectric constant (k value) in a range of about 2.5 to about 6.0;
• a first conductor and a second conductor in the first trench and the second trench, respectively;
• an etch stop layer over the first conductor, the second conductor, and the dielectric liner;
• a removed portion of the first dielectric layer between the first conductor and the second conductor, the removed portion exposing respective portions of the dielectric liner lining the first trench and the dielectric liner lining the second trench;
• and
• a second dielectric layer over the etch stop layer, the second dielectric layer having an air gap therein between the first conductor and the second conductor.