A method for forming an interconnect structure is provided. The method includes providing a substrate with a surface; and forming a metal layer covering the surface of the substrate and with a desired grain size to reduce grain boundary scattering of the interconnect structure subsequently formed with the metal layer. The method also includes etching the metal layer to form a plurality of metal lines on the surface of the substrate and a plurality of metal pillars on each of the plurality of the metal lines of the interconnect structure; and forming a dielectric layer covering the surface of the substrate, surfaces of the metal lines, and side surfaces of the metal pillars.