An interconnection structure fabrication method is provided. The method includes providing a substrate; forming a conductive film with a first thickness and having a first lattice structure and a first grain size, wherein the first thickness is greater than the first grain size; and performing an annealing process to change the first lattice structure of the conductive film to a second lattice structure and to change the first grain size to a second grain size. The second grain size is greater than the first grain size, and the first thickness is greater than or equal to the second grain size. The method also includes etching portion of the conductive film to form at least one conductive layer; etching portion of the conductive layer to form at least one trench having a depth smaller than the first thickness in the conductive layer to form an electrical interconnection wire and conductive vias; and forming a dielectric layer covering the substrate, sidewalls of the conductive layer, and the trench.