METHOD FOR FORMING DUAL TRENCH OF FLASH MEMORY DEVICE

摘要

PURPOSE: A method for forming a dual trench of a flash memory device is provided to conserve the isolation characteristics of a peripheral region and reduce the surface area of a peripheral region trench by forming trenches having different depths according to a cell region and the peripheral region. CONSTITUTION: A semiconductor substrate(200) is defined with a cell region(A) and a peripheral region(B). A cell region trench(208) and a peripheral region trench pattern are simultaneously formed by selectively removing the semiconductor substrate. At this time, the trenches have the same depth. A protecting layer is coated on the cell region. Then, a peripheral region trench(211) having the second depth is formed by carrying out an etching process using the protecting layer as an etching mask. A predetermined insulating layer is deposited on the resultant structure for filling the trenches.