A method of forming a via contact structure using a dual damascene process is disclosed. According to one embodiment a sacrificial layer is formed on an insulating interlayer during the formation of a preliminary via hole. The sacrificial layer has the same composition as a layer filling the preliminary via hole in a subsequent trench formation process. The sacrificial layer and the layer filling the preliminary via hole are simultaneously removed after the trench formation process is carried out. According to another embodiment, a thin capping oxide layer is formed on an insulating interlayer during the formation of a preliminary via hole. The thin capping oxide layer is removed together with a sacrificial layer after a trench formation process is carried out.