Resistance variable memory structure and method of forming the same

A semiconductor structure comprising:

• a memory region;
• and
• a memory structure disposed on the memory region, the memory structure comprising:
• a first electrode having a top surface, a bottom surface, and a first outer sidewall surface extending from the top surface to the bottom surface, wherein the first outer sidewall is a single lateral edge extending substantially perpendicular to the top surface;
• a resistance variable layer having at least a first portion and a second portion, wherein the first portion is disposed directly on the top surface of the first electrode and the second portion extends upwardly from the first portion and has a second outer sidewall surface;
• a protection material layer surrounding the resistance variable layer, wherein the protection material layer is a substantially oxygen free material extending from a top surface of the protection material layer to a bottom surface of the protection material layer, where the protection material layer interfaces with a first portion of the first outer sidewall surface, and wherein the bottom surface of the first electrode is disposed below a bottom surface of the protection material layer, the resistance variable layer is in direct contact with the substantially oxygen free material of the protection material layer;
• and
• a second electrode disposed over the resistance variable layer, wherein the second electrode forms an interface with the first portion, and wherein a top surface of the second electrode is coplanar with the top surface of the protection material layer.

A method of forming a resistance variable memory structure, the method comprising:

• forming a protection material over a conductive structure and an etch stop layer;
• etching an opening in the protection material and the etch stop layer to expose a portion of the conductive structure, the opening having a sidewall surface;
• partially filling the opening with a first electrode material over the conductive structure to form a first electrode, the first electrode having a top surface and a first outer surface substantially aligned with the sidewall surface of the opening, wherein a lowest portion of the first electrode is below a lowest portion of the protection material;
• depositing a resistance variable layer in the opening over the first electrode, wherein the resistance variable layer has a first portion over the top surface of the first electrode, and a second portion extending upwardly from the first portion and having a second outer surface substantially aligned with sidewall surface of the opening;
• forming a second electrode material over the resistance variable layer;
• patterning the second electrode material and the resistance variable layer to form a second electrode over the first electrode, wherein the second electrode forms an interface with the first portion;
• and
• after forming the second electrode material, removing a portion of the protection material to expose a portion of the etch stop layer.