Patent ID: 8026140

Claim:
A method of forming a flash memory device, the method comprising: forming a screen insulating layer on a semiconductor substrate; forming isolation mask patterns over the screen insulating layer; forming trenches by performing an etching process using the isolation mask patterns; forming isolation layers by filling the trenches with an insulating layer; removing the isolation mask patterns to expose the screen insulating layer, thereby protruding a portion of the isolation layers upwardly from the semiconductor substrate; cleaning the protruded isolation layers and the screen insulating layer so that a portion of the protruded isolation layers is etched and the screen insulating layer partially remains; forming a tunnel dielectric layer along surface of the resultant structure including the protruded isolation layers; forming a first crystallized floating gate along a surface of the tunnel dielectric layer and the protruded isolation layers, wherein the first crystallized floating gate is an undoped polysilicon layer; forming a second crystallized floating gate over the first crystallized floating gate to fill a gap between the protruded isolation layers, wherein the second crystallized floating gate is a doped polysilicon layer; performing a polishing process to expose the protruded isolation layers; and sequentially forming a dielectric layer and a control gate over a resulting structure after performing the polishing process.