Aligning conductive vias with trenches

A method for forming conductive contacts on a semiconductor wafer, the method comprising:

• forming a hardmask on an insulator layer, a planarizing layer on the hardmask and a layer of sacrificial mandrel material on the planarizing layer;
• removing portions of the layer of sacrificial mandrel material to expose portions of the planarizing layer and form a first sacrificial mandrel and a second sacrificial mandrel on the planarizing layer;
• depositing a layer of spacer material over the planarizing layer, the first sacrificial mandrel and the second sacrificial mandrel;
• depositing a first filler material over the layer of spacer material;
• patterning a first mask over the filler material;
• removing portions of the first filler material to expose a portion of the layer of spacer material over a portion of the first sacrificial mandrel and removing the mask;
• removing a portion of the layer of spacer material and an exposed portion of the first sacrificial mandrel to form a first cavity that exposes a portion of the planarizing layer;
• filling the first cavity with a second filler material;
• patterning a second mask over the first filler material;
• removing portions of the first filler material to form a second cavity that exposes portions of the layer of spacer material between the first cavity and the second sacrificial mandrel;
• filling the second cavity with the second filler material;
• patterning a third mask over a portion of the second sacrificial mandrel;
• selectively removing exposed portions of the second filler material, a portion of the layer of spacer material, the planarizing layer and the hardmask to form a third cavity;
• patterning a fourth mask over a portion of the second sacrificial mandrel;
• removing an exposed portion of the second sacrificial mandrel, a portion of the planarizing layer and a portion of the hardmask to form a fourth cavity;
• removing exposed portions of the insulator layer to increase a depth of the third cavity and a depth of the fourth cavity;
• and
• filling the third cavity and the fourth cavity with a conductive material.