A method of forming a memory device. The method provides a
semiconductor substrate having a surface region. A first
dielectric layer is formed overlying the surface region of the
semiconductor substrate. A bottom wiring structure is formed overlying the first
dielectric layer and a second
dielectric material is formed overlying the top wiring structure. A bottom
metal barrier material is formed to provide a
metal-to-
metal contact with the bottom wiring structure. The method forms a pillar structure by patterning and
etching a material stack including the bottom metal barrier material, a contact material, a switching material, a conductive material, and a top barrier material. The pillar structure maintains a metal-to-metal contact with the bottom wiring structure regardless of the alignment of the pillar structure with the bottom wiring structure during
etching. A top wiring structure is formed overlying the pillar structure at an angle to the bottom wiring structure.