Provided is a method of forming an interconnect structure including: forming a via; forming a first barrier layer to at least cover a top surface and a sidewall of the via; forming a first dielectric layer on the first barrier layer; performing a planarization process to remove a portion of the first dielectric layer and a portion of the first barrier layer, thereby exposing the top surface of the via; forming a second dielectric layer on the first dielectric layer, wherein the second dielectric layer has an opening exposing the top surface of the via; forming a blocking layer on the top surface of the via; forming a second barrier layer on the second dielectric layer; removing the blocking layer to expose the top surface of the via; and forming a conductive feature in the opening, wherein the conductive feature is in contact with the top surface of the via.