Semiconductor memory structures

A semiconductor structure, comprising:

• a transistor over a. substrate, the transistor comprising a gate and a contact region adjacent to the gate and within the substrate;
• a first dielectric layer over the contact region;
• a conductive contact structure within the first dielectric layer and over the contact region;
• a first electrode within the first dielectric layer;
• a second dielectric layer over the first electrode;
• a phase change structure within the second dielectric layer, the phase change structure comprising:
• at least one conductive sidewall spacer within the second dielectric layer and having a bottom portion with a greater thickness than a top portion thereof;
• and
• a phase change material (PCM) layer on top of an upper surface of the conductive spacer;
• a second electrode over the phase change structure;
• and
• a third dielectric layer over the PCM layer, wherein a top surface of the third dielectric layer is substantially coplanar with a top surface of the second dielectric layer.

A semiconductor structure, comprising:

• a transistor over a substrate, the transistor comprising a gate and a contact region adjacent to the gate and within the substrate;
• a first dielectric layer over the contact region;
• a contact structure within the first dielectric layer and over the contact region;
• a first electrode within the first dielectric layer;
• a second dielectric layer over the first electrode;
• a phase change structure within the second dielectric layer, the phase change structure comprising:
• spacers within the second dielectric layer;
• a conductive layer extending from a first one of the spacers to a second one of the spacers and extending vertically along and directly contacting sidewalls of said spacers;
• and
• a phase change material (PCM) layer over the conductive layer and laterally spaced from the spacers by the conductive layer;
• and
• a second electrode over the phase change structure, wherein said conductive layer comprises one of titanium tungsten (TiW), tungsten (W), platinum (Pt), platinum iridium (Ptlr), copper (Cu), aluminum (Al), aluminum copper (AICu), and aluminum silicon copper (AlSiCu).