Semiconductor devices and methods of manufacture thereof are disclosed. In some embodiments, a method of manufacturing a semiconductor device includes forming an insulating material layer over a workpiece, patterning an upper portion of the insulating material layer with a conductive line pattern, and forming a stop layer comprising a metal oxide or a metal nitride over the patterned insulating material layer. A masking material is formed over the stop layer, and the masking material is patterned with a via pattern. The via pattern of the masking material is transferred to a lower portion of the insulating material layer.