Hybrid metal interconnects with a bamboo grain microstructure

A method for forming an interconnect with a bamboo grain microstructure, comprising:

• depositing at least one conformal layer in a trench of an insulating layer such that the at least one conformal layer protects the insulating layer;
• forming conductive filler layer in a bottom portion of the trench to a predetermined depth such that an aspect ratio of a top portion of the trench is reduced from an initial aspect ratio, the aspect ratio being approximately 1:1 or less, wherein the predetermined depth is less than a full depth of the trench;
• depositing a metal layer in the top portion of the trench over the conductive filler layer, the metal layer having a plurality of small grains;
• and
• annealing the metal layer to provide a bamboo grain microstructure having larger grains than grain boundaries of the plurality small grains.