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 a TaN/Ta (TNT) barrier and a Cu overfill. The structures were the planarized by CMP. In this way, narrow structures wereentirely filled by Ru whereas larger structures were filled by a Ru/Cu combination.