Method of forming floating gate of flash memory

A method of forming the floating gate of a flash memory unit, comprising the steps of:

• forming a tunnel oxide layer and a first floating gate layer over a substrate;
• patterning the first floating gate layer, the tunnel oxide layer and the substrate to form an opening:
• forming a first dielectric layer over the substrate and interior surface of the opening but without completely filling the opening;
• forming a second dielectric layer over the first dielectric layer so that the opening is completely filled;
• planarizing the second dielectric layer to expose the first dielectric layer;
• removing a portion of the first dielectric layer to expose the first floating gate layer;
• forming a second floating gate layer that covers the first dielectric layer, the second dielectric layer and the first floating gate layer;
• and
• planarizing the second floating gate layer to expose the first dielectric layer.