Techniques are provided to fabricate metallic interconnect structures in a single metallization level, wherein different width metallic interconnect structures are formed of different metallic materials to eliminate or minimize void formation in the metallic interconnect structures. For example, a semiconductor device includes an insulating layer disposed on a substrate, and a first metallic line and a second metallic line formed in the insulating layer. The first metallic line has a first width, and the second metallic line has a second width which is greater than the first width. The first metallic line is formed of a first metallic material, and the second metallic line is formed of a second metallic material, which is different from the first metallic material. For example, the first metallic material is cobalt or ruthenium, and the second metallic material is copper.