Flash memory cell with a flair gate
View Patent ↗An embodiment of the present invention is directed to a method of forming a memory cell. The method includes etching a trench in a substrate and filling the trench with an oxide to form a shallow trench isolation (STI) region. A portion of an active region of the substrate that comes in contact with the STI region forms a bitline-STI edge. The method further includes forming a gate structure over the active region of the substrate and over the STI region. The gate structure has a first width substantially over the center of the active region of the substrate and a second width substantially over the bitline-STI edge, and the second width is greater than the first width.
1. A method of forming a memory cell, the method comprising:
forming a charge trapping layer over a substrate wherein the charge trapping layer comprises an oxide-nitride-oxide layer or an oxide-Silicon Rich Nitride-oxide layer;
etching a trench in the charge trapping layer and the substrate;
filling the trench with an oxide to form a shallow trench isolation (STI) region, wherein a portion of an active region of the substrate that comes in contact with the STI region forms a bitline-STI edge;
masking the charge trapping layer with a mask, wherein the mask has a first width substantially over the center of the active region of the substrate and a second width that is centered above the STI region and extends substantially over the bitline-STI edge, wherein the second width is greater than the first width and wherein portions of adjacent gate structures of the second width extend across separate portions of the same bitline;
etching the charge trapping layer; and
removing the mask.
2. The method as recited in claim 1 further comprising:
masking the charge trapping layer before said etching.
3. The method as recited in claim 1 wherein the memory cell is a NAND memory cell.
4. The method as recited in claim 1 further comprising:
forming a polysilicon layer over the charge trapping layer and the STI region.
5. The method as recited in claim 1 further comprising:
polishing the memory cell with a CMP process.