A structure of semiconductor device includes a substrate. An interconnection layer is formed on the substrate including a first inter-layer dielectric (ILD) layer over the substrate. A lower wiring structure is formed in the ILD layer. A hard mask layer is disposed on the first ILD layer. The hard mask layer has a first opening and a second opening being adjacent to expose the lower wiring structure. A second ILD layer is disposed on the hard mask layer. The second ILD layer has a via opening aligned to the first opening of the mask layer and a trench pattern connecting with the via opening. The second ILD layer has a protruding portion to fill the second opening of the mask layer. A metal line layer fills the via opening and the trench pattern in the second ILD layer and the first opening of the hard mask layer.