Via structure, mram device using the via structure and method for fabricating the mram device

A device, comprising:

• a transistor;
• a first dielectric layer over the transistor;
• a contact in the first dielectric layer and electrically connected to the transistor;
• a bottom etch stop layer over the first dielectric layer;
• a top etch stop layer over the bottom etch stop layer, wherein a thickness of the bottom etch stop layer is equal to or smaller than a thickness of the top etch stop layer;
• a second dielectric layer over the top etch stop layer;
• a memory stack over the second dielectric layer;
• and
• a via structure in the second dielectric layer, the top etch stop layer, and the bottom etch stop layer and electrically connecting the memory stack and the contact.

A method, comprising:

• depositing a first dielectric layer over a transistor;
• forming a contact in the first dielectric layer and electrically connected to the transistor;
• depositing a metal nitride layer over the first dielectric layer and the contact;
• depositing an etch stop layer over the metal nitride layer;
• depositing a second dielectric layer over the etch stop layer;
• forming a via structure in the second dielectric layer, the etch stop layer, and the metal nitride layer and landing on the contact;
• and
• forming a memory stack over the via structure.