Stacked-gate flash memory cell with folding gate and increased coupling ratio

A stacked-gate flash memory having a shallow trench isolation with a high-step oxide and high lateral coupling comprising:

• a substrate having a surface;
• at least two trenches, each of said trenches formed in said surface of said substrate to a depth between about 2500 to 5000 Å below the surface of said substrate;
• an oxide layer formed on the walls and bottom of each said trench;
• a high-step isolation oxide formed over said oxide layer within each of said trenches and protruding vertically upward from said surface of said substrate to a height between about 2000 to 6000 Å;
• a contiguous pair of said high-step isolation oxides forming an opening in the space over said surface of said substrate between said pair of high-step isolation oxides, said opening having vertical interior walls;
• a gate oxide formed on said surface of said substrate between said contiguous pair of said high-step isolation oxides;
• a first conductive layer formed conformally on said gate oxide within said opening and on said interior walls of said opening and extending above said opening, said first conductive layer having an interior surface within the opening, said first conductive layer having internal, external and top surfaces above said opening, said first conductive layer functioning as a floating gate residing completely within said opening;
• an intergate oxide layer conformally formed over said external, top and internal surfaces of said first conductive layer, said intergate oxide layer thus having external, top and internal surfaces;
• a second conductive layer formed over said intergate oxide layer protruding downward in between said internal and external surfaces of said intergate oxide layer, said second conductive layer forming a control gate having high lateral coupling with said floating gate;
• and a self-aligning source line.