FLASH MEMORY DEVICE MANUFACTURING METHOD

PROBLEM TO BE SOLVED: To provide a method for manufacturing a flash memory device that prevents a thin tunnel oxide film from being formed at the upper corner of a trench during device separation film formation to which the STI process applies. SOLUTION: A screen oxide film 11 and a pad nitride film 12 formed on a semiconductor substrate 10 are patternized and a spacer 14a is formed at a double-layered sidewall. Then, the above semiconductor substrate 10 is oxidized, a surface oxide film is formed at the top and bottom of the above semiconductor substrate 10 to be exposed, and trench etching is performed to form a trench on the above semiconductor substrate 10. To form a tunnel oxide film, an insulation film for the device separation film is formed in a way that the above trench is buried; the above pad nitride film 12 is removed; the above spacer 14a and the above screen oxide film 11 are removed; a part of the above insulation film for the device separation film is etched for device separation film formation; and then the overall structure including the above device separation film is oxidized. COPYRIGHT: (C)2006,JPO&NCIPI