Front to back resistive random-access memory cells

A method for forming a resistive random-access memory device on a semiconductor substrate, the method comprising:

• forming a first interlayer dielectric on the semiconductor substrate;
• forming a chemical-mechanical-polishing stop layer over the first interlayer dielectric;
• forming a first via through the chemical-mechanical-polishing stop layer and the first interlayer dielectric;
• forming a lower metal layer in the first via, the lower metal layer serving as an ion source, a top surface of the lower metal layer extending above a top surface of the chemical-mechanical-polishing stop layer;
• forming a solid electrolyte layer over the lower metal layer in the first via, the solid electrolyte layer extending over the chemical-mechanical-polishing stop layer and extending beyond outer edges of the first via;
• forming a barrier metal layer over the solid electrolyte layer, edges of the barrier metal layer extending beyond outer edges of the first via;
• forming a second interlayer dielectric over the barrier metal layer, the second interlayer dielectric including a second via formed therethrough communicating with the barrier metal layer;
• and
• forming an upper metal layer in the second via.