| 摘要 |
PURPOSE: A method for forming a trench is provided to be capable of exactly controlling the depth of the trench by using a dual hard mask including a silicon nitride layer and a polysilicon layer. CONSTITUTION: A pad oxide layer(21), a silicon nitride layer and a polysilicon layer are sequentially formed on a silicon substrate(20). The stacked structure is then patterned using a photoresist pattern as a mask. After removing the photoresist pattern, a trench is then formed by using the silicon nitride pattern(22) and the polysilicon pattern as a dual hard mask. An isolation layer(25') is formed by filling an oxide layer into the trench and planarizing.
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