Interconnect structures are provided. An exemplary embodiment of an interconnect structure comprises a substrate with a low-k dielectric layer thereon. A via opening and a trench opening are formed in the low-k dielectric layer, wherein the trench opening is formed over the via opening and the via opening exposes a portion of the substrate. A liner layer is formed on sidewalls of the low-k dielectric layer exposed by the trench and via protions and a bottom surface exposed by the trench via portion, wherein the portion of the liner layer on sidewalls of the low-k dielectric layer exposed by the trench and via protions and the portion of the liner layer formed on a bottom surface exposed by the trench portion comprise different materials. A conformal conductive barrier layer is formed in the trench and via openings, covering the liner layer and the exposed portion of the substrate. A conductive layer is formed on the conductive barrier layer, filling in the trench and via openings.