Interconnect structures and methods of forming same

A device comprising:

• a first low-k dielectric layer comprising a first conductive feature;
• a second low-k dielectric layer over the first low-k dielectric layer;
• a reinforcement layer over the second low-k dielectric layer;
• a third low-k dielectric layer over the reinforcement layer, wherein the third low-k dielectric layer has a lower dielectric constant than the reinforcement layer;
• and
• a second conductive feature extending through the second low-k dielectric layer, the reinforcement layer, and the third low-k dielectric layer, wherein a portion of the reinforcement layer is disposed between the third low-k dielectric layer and the second conductive feature, and wherein the second conductive feature comprises:
• a conductive line;
• a top conductive via portion smoothly connected to the conductive line;
• a conductive barrier layer on sidewalls of the conductive line and the top conductive via portion;
• and
• a bottom conductive via portion comprising a different material than the top conductive via portion, wherein the conductive barrier layer is disposed between the top conductive via portion and the bottom conductive via portion.

A method for forming a semiconductor device, the method comprising:

• patterning a via opening in one or more dielectric layers, wherein the via opening exposes a first conductive feature under the one or more dielectric layers;
• patterning a trench opening in the one or more dielectric layers, wherein the trench opening is connected to the via opening;
• and
• forming a second conductive feature in the one or more dielectric layers and electrically connected the first conductive feature, wherein forming the second conductive feature comprises:
• electroless plating at least about twenty percent of the via opening with a first conductive material;
• depositing a conductive barrier layer in the via opening and over the first conductive material;
• and
• filling the trench opening and a remaining portion of the via opening with a second conductive material different from the first conductive material, wherein the conductive barrier layer is disposed between the first conductive material and the second conductive material along a line perpendicular to a top surface of the first conductive material.