On/off ratio for nonvolatile memory device and method

A method, comprising:

• forming a structure comprising a switching material, the structure overlying a first wiring structure and having a top region and a side region, the top region comprises a surface of the switching material;
• depositing a first dielectric layer onto the structure, the first dielectric layer covers the surface of the switching material and comprises a first dielectric material;
• forming an opening in the first dielectric layer, the opening exposes a first portion of the surface of the switching material;
• depositing a second dielectric layer onto the first dielectric layer, the second dielectric layer fills a portion of the opening and comprises a second dielectric material;
• forming a second opening in the second dielectric layer, the second opening exposes a second portion of the surface of the switching material smaller than the first portion, a portion of the second dielectric layer in proximity to the second opening defines a spacer structure in contact with a surface of the first dielectric layer and a third portion of the surface of the switching material;
• covering a surface of the spacer structure and the second portion of the surface of the switching material with a conductive material;
• and
• forming a second wiring structure comprising the conductive material.