METHOD FOR FABRICATING FLASH MEMORY DEVICE

摘要

A method for manufacturing a flash memory device is provided to improve polishing speed in a CMP process of a poly silicon layer for a floating gate, to prevent generation of a poly residue, and to protect a surface of a floating gate by removing a natural oxide layer generated on the surface of the poly silicon layer. A pad oxide layer and a pad nitride layer are formed on a semiconductor substrate(20) having a cell region and a peri region. The pad nitride, the pad oxide layer, and the semiconductor substrate are etched to form a trench. An isolation layer(24a) is formed in the trench. The pad nitride layer and the pad oxide layer are removed to make an upper portion of the isolation layer be projected on a surface of the semiconductor substrate. A width of the isolation layer is reduced. A tunnel oxide layer(25) is formed on the semiconductor substrate exposed by removing the pad oxide layer. A poly silicon layer is formed on the whole surface. A natural oxide layer formed on a surface of the poly silicon layer is removed. A floating gate(26a) is formed by performing CMP on the poly silicon layer to expose the isolation layer.