METHOD FOR FABRICATING FLASH MEMORY DEVICE HAVING SHALLOW TRENCH ISOLATION(STI) STRUCTURE

摘要

PURPOSE: A method for fabricating a flash memory device having a shallow trench isolation(STI) structure is provided to prevent the deterioration of the device characteristics due to a dent and a bird's beak formed at an edge of an active region. CONSTITUTION: After forming a gate oxide(44) on a semiconductor substrate(42), the first conductive layer(46) for a floating gate is formed by depositing a polysilicon film. After forming a mask layer(48) by depositing a nitride film, the gate oxide is revealed by etching the mask layer and the first conductive layer anisotropically in sequence using a photo lithography process. Then, the first buffer layer(50) and an anti-oxidation film(52) are formed on a side wall of the first conductive layer and the mask layer, by etching back a MTO(Middle Temperature Oxide) and a nitride film. A trench(54) is formed on a part where an isolation film is to be formed using the mask layer and the first buffer layer and the anti-oxidation film as a mask. Then an inner oxide(56) is formed on an inner wall of the trench using a thermal oxidation process. And the second buffer layer(58) is formed by depositing an MTO and a liner(60) is formed by depositing a thin nitride film. Then the trench is filled with an insulation film like a USG(Undoped Silica Glass) or an HDP(High Density Plasma) on the resulted structure.