Structure and method of forming a dual damascene structure

A structure and a method for forming a semiconductor device structure is provided. The semiconductor device structure includes a semiconductor substrate and a conductive feature on the semiconductor substrate. The semiconductor device structure also includes a dielectric layer over the conductive feature and the semiconductor substrate and a via hole in the dielectric layer. The via hole has an oval cross-section. The semiconductor device structure further comprises a trench in the dielectric layer, and the via hole extending from a bottom portion of the trench. The trench has a grave width which is wider than a hole width of the via hole. In addition, the semiconductor device structure comprises one or more conductive materials which fill the via hole and the trench, and are electrically connected to the conductive feature.