METHOD OF MANUFACTURING FLASH MEMORY DEVICE FOR IMPROVING DIFFERENCE OF EFFECTIVE FIELD OXIDE HEIGHT BETWEEN HIGH VOLTAGE TRANSISTOR REGION AND LOW VOLTAGE TRANSISTOR/CELL REGION

摘要

PURPOSE: A method of manufacturing a flash memory device is provided to improve the difference of EFH(Effective Field oxide Height) between a high voltage transistor region and a low voltage transistor/cell region. CONSTITUTION: A gate oxide layer, a first polysilicon layer(23) and a nitride layer(24) are sequentially formed on a semiconductor substrate(21) with a high voltage transistor region(HV) and a low voltage transistor/cell region(LV/CELL). A plurality of trenches(25) are formed in the resultant structure by using an SA-STI(Self Align-Shallow Trench Isolation) scheme. An oxide layer for filling completely the trenches are formed thereon. The oxide layer is polished until the first polysilicon layer of the high voltage transistor region is nearly exposed to the outside, so that isolation layers(260) are completed. The isolation layer of the low voltage transistor/cell region is partially removed therefrom. The nitride layer is then removed therefrom and a first and second polysilicon layer are sequentially formed thereon.