Semiconductor device having a self-forming barrier layer at via bottom

A method for forming a barrier layer in a semiconductor device, comprising:

• selectively applying the barrier layer along a bottom surface only of a via of the semiconductor device, the via being formed through an ultra low k a dielectric layer and a cap layer of the semiconductor device;
• applying a liner layer over the barrier layer and along a set of sidewalls of the via;
• filling the via with a metal;
• and
• processing the semiconductor device to remove the liner layer from over the barrier layer.

A semiconductor device, comprising:

• a first metal layer;
• a cap formed over the first metal layer;
• an ultra low k a dielectric layer formed over the cap layer;
• and
• a via formed through the ultra low k dielectric layer and the cap layer, the via comprising a barrier layer selectively formed along a bottom surface only of the via, and a liner layer along a set of sidewall sidewalls of the via.