Process for producing a semiconductor memory device comprising mass-storage memory cells and shielded memory cells for storing reserved information

A method for producing a shielded non-volatile memory device comprising the steps of:

• forming a first non-volatile memory cell on a semiconductor substrate, the first non-volatile memory cell having a control gate and a floating gate;
• forming a second non-volatile memory cell on the semiconductor substrate, the second non-volatile cell having first and second polysilicon gate layers superimposed on one another;
• and
• covering the control and floating gates of the first memory cell with a shielding polysilicon layer formed by the second polysilicon gate layer of the second non-volatile memory cell.

A process for forming a semiconductor memory device comprising:

• on a semiconductor substrate, forming a dielectric layer for a non-volatile first memory cell and a non-volatile second memory cell;
• forming a gate layer on the dielectric layer for the first and second memory cells;
• covering the gate layer with an intermediate insulating layer for the first and second memory cells;
• forming a floating gate of the first memory cell from the gate layer;
• forming a control gate of the first memory cell, the control gate being capacitively coupled to the floating gate;
• after forming the control gate of the first memory cell, forming a shielding layer on a portion of the intermediate insulating layer for the first memory cell using a conductive layer;
• and
• forming a control gate on a portion of the intermediate insulating layer for the second memory cell using the conductive layer.