Phase-change memory and method of forming same

A device comprising:

• a substrate;
• a first dielectric layer over the substrate;
• a conductive line in the first dielectric layer;
• a second dielectric layer over the conductive line and the first dielectric layer;
• a bottom electrode within the second dielectric layer, the bottom electrode being electrically connected to the conductive line, the bottom electrode having a first width;
• a first buffer layer over the bottom electrode, the first buffer layer having a second width;
• a phase-change layer over the first buffer layer, the phase-change layer having a third width greater than the first width;
• a top electrode over the phase-change layer, the top electrode having the third width;
• a third dielectric layer over the second dielectric layer, the third dielectric layer extending along sidewalls of the phase-change layer and sidewalls of the top electrode;
• a fourth dielectric layer over the third dielectric layer and the top electrode;
• and
• a conductive via within the fourth dielectric layer, the conductive via being electrically connected to the top electrode.

A method comprising:

• forming a first dielectric layer over a substrate;
• forming a first conductive feature in the first dielectric layer;
• forming a second dielectric layer over the first dielectric layer and the first conductive feature;
• forming an opening in the second dielectric layer, the opening exposing a topmost surface of the first conductive feature;
• filling the opening with a first conductive material to form a bottom electrode in the second dielectric layer;
• depositing a phase-change material over the second dielectric layer and the bottom electrode;
• depositing a first buffer material over the phase-change material;
• depositing a second conductive material over the first buffer material;
• performing a patterning process to remove a portion of the phase-change material, a portion of the first buffer material and a portion of the second conductive material and to expose a topmost surface of the second dielectric layer, a remaining portion of the phase-change material forming a phase-change layer, a remaining portion of the first buffer material forming a first buffer layer, a remaining portion of the second conductive material forming a top electrode;
• and
• forming a third dielectric layer over the second dielectric layer, the third dielectric layer surrounding the first buffer layer, the phase-change layer and the top electrode.