When forming metal lines of the metal zero level, a reduced bottom width and an increased top width may be achieved by using appropriate patterning regimes, for instance using a spacer structure after forming an upper trench portion with a top width, or forming the lower portion of the trenches and subsequently applying a further mask and etch regime in which the top width is implemented. In this manner, metal lines connecting to self-aligned contact bars may be provided so as to exhibit a bottom width of 20 nm and less, while the top width may allow reliable contact to any vias of the metallization system.