Method for fabricating flash memory

A method for fabricating flash memory, comprising:

• providing a substrate defining a memory device region and a logic device region, wherein the memory device region comprises a plurality of cell areas;
• forming a gate dielectric layer on the memory device region and the logic device region of the substrate;
• forming a plurality of floating gate structures on the gate dielectric layer disposed on the memory device region, wherein each of the cell areas is formed with two floating gate structures, and each of the floating gate structures comprises a floating gate layer and a polysilicon oxide layer on the floating gate layer;
• depositing an insulating layer to cover the gate dielectric layer and the floating gate structures;
• etching back the insulating layer, and keeping a part of the insulating layer as protective spacers on two opposite sidewalls of each floating gate structure;
• forming a polysilicon layer to cover the gate dielectric layer, the floating gate structures and the protective spacer;
• forming a hard mask layer to cover the polysilicon layer;
• removing a part of the hard mask layer and a part of the polysilicon layer to form at least one polysilicon gate structure on the logic device region, and to form a polysilicon control gate structure on each cell area to cover two adjacent floating gate structures on each cell area, wherein the polysilicon control gate structure comprises an opening to at least expose the two protective spacers facing each other between two adjacent floating gate structures;
• removing the exposed protective spacer;
• and
• performing an ion implantation on the substrate to form a source region between the two adjacent floating gate structures on each cell area.