1. A switching device, comprising: a structure comprising a switching material, the structure overlies a first wiring structure and has a top region and a side region, the top region comprises a surface of the switching material; a dielectric layer that defines an opening and overlies the structure, the dielectric layer comprises a first dielectric material; a spacer structure disposed within the opening and in contact with a surface of the dielectric layer and a first portion of the surface of the switching material, the spacer structure defines a second opening and comprises a second dielectric material, the second opening exposes a second portion of the surface of the switching material, the first portion having larger surface area than the second portion; a conductive material that overlies the spacer structure and covers a portion of the second opening, the conductive material is in contact with the second portion of the surface of the switching material; and a second wiring structure that overlies the conductive material.