The Ru ALD process described above was used to fill single damascene lines with 10 nm target dimension. The metallization scheme is represented in Fig. 3. Initially, Ru was deposited on top of a 0.3 nm ALD TiN adhesion layer into (sub-)10 nm wide trenches in SiO2. This was followed by aTaN/Ta (TNT) barrier and a Cu overfill. The structures were the planarized by CMP. In this way, narrow structures were entirely filled by Ru whereas larger structures were filled by a Ru/Cu combination.