Structure of memory device and fabrication method thereof

A structure of memory device, comprising:

• a substrate, comprising a bottom electrode layer therein;
• a buffer layer, disposed on the substrate, in contact with the bottom electrode layer;
• a resistive layer, surrounding a whole sidewall of the buffer layer and extending upward vertically from the substrate, wherein the bottom electrode layer contacts with the buffer layer but does not contact with the resistive layer;
• a mask layer, disposed on the buffer layer and the resistive layer;
• a noble metal layer, disposed over the substrate and fully covering sidewalls of the resistive layer and sidewalls and top of the mask layer;
• and
• a top electrode layer, disposed on the noble metal layer.