Metal interconnect structure and method for fabricating the same

A method for fabricating semiconductor device, comprising:

• forming a dielectric layer on a substrate;
• forming a trench in the dielectric layer;
• forming a second liner in the trench;
• forming a third liner on the second liner, wherein the second liner and the third liner comprise different thicknesses and different materials;
• performing an anneal process to transform the second liner and the third liner into a first liner in the trench, wherein the first liner comprises Co—Ru alloy;
• forming a metal layer on the first liner, wherein the Co—Ru alloy contacts the metal layer directly;
• and
• planarizing the metal layer and the first liner to form a metal interconnection.