| 摘要 |
PURPOSE: A method for fabricating a flash memory device is provided to increase erase efficiency by making the edge of a floating gate sharp, and to expand a contact surface of a control gate and the floating gate by decreasing the thickness of an oxide layer between a control gate and the floating gate and by etching the control gate and the floating gate by a self-aligned way. CONSTITUTION: After a gate oxide layer(102) is grown on a semiconductor substrate(101), a nitride layer is deposited. Photoresist is applied to the surface of the resultant structure and is patterned. The nitride layer in a floating gate formation region is selectively etched by using the photoresist as an etch mask. The photoresist is eliminated. The first polysilicon layer(105) is deposited to form the floating gate on the resultant structure such that the center of the first polysilicon layer has a concave type in the floating gate formation region due to the difference of the nitride layer. After photoresist is formed and patterned, the first polysilicon layer is selectively etched. The nitride layer is selectively wet-etched to finish the floating gate whose edge region is sharp due to the concave type. The second polysilicon layer(107) is deposited to form a tunnel oxide layer(106) and a control gate on the resultant structure. A patterning and etch process is performed according to a desired critical dimension(CD) to self-align the control gate and the floating gate.
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