The present disclosure provides an interconnect structure, including a substrate having a conductive region adjacent to a gate region, a contact over the conductive region, a first interlayer dielectric layer (ILD) surrounding the contact, a via over the contact, a first densified dielectric layer surrounding the via, wherein the densified dielectric layer has a first density, and a second ILD layer over the first ILD layer and surrounding the via, wherein the second ILD layer has a second density, the first density is greater than a second density.