METHOD FOR FABRICATING FLASH MEMORY DEVICE

摘要

PURPOSE: A method for fabricating a flash memory device is provided to improve uniformity of an oxide layer in a peripheral circuit region by sufficiently performing a pre-cleaning process regarding a gate oxide layer, and to improve a cell characteristic by making a cover polysilicon layer protect a dielectric layer in a cell region. CONSTITUTION: A semiconductor substrate(31) is prepared in which the peripheral circuit region and the cell region are defined. A tunnel oxide layer(33a) and the first polysilicon layer(34) for a floating gate are formed in the cell region. A dielectric layer(35) is formed. The second polysilicon layer(37) for protecting and planarizing the dielectric layer is formed and etched back to planarize the upper portion of the second polysilicon layer. The second polysilicon layer and the dielectric layer in the peripheral circuit region are removed to expose the surface of the substrate by an etch process. A gate oxide layer(33b) for high voltage and a gate oxide layer(33c) for low voltage are formed in the peripheral circuit region while the upper portion of the second polysilicon layer in the cell region is oxidized to form a polysilicon oxide layer. The third polysilicon layer for a gate electrode is formed in the peripheral circuit region. The third polysilicon layer and the polysilicon oxide layer in the cell region are eliminated. A top polysilicon layer(38) and a tungsten silicide layer(39) are sequentially formed and patterned.