| 摘要 |
PURPOSE: A method for manufacturing a semiconductor device is provided to prevent thinning of a gate oxide layer at edge portions of STI(Shallow Trench Isolation) by releasing compressive stress concentrated on the side of STI. CONSTITUTION: After forming pad-oxide/nitride/oxide layer structure on an active region of a substrate(200), a LOCOS oxide layer having bird's beaks(210a,210b) is formed in a field region. A trench is formed in the field region by etching the LOCOS oxide layer and the substrate at a desired depth. A CVD oxide layer(212a) is formed to fill the trench sufficiently. An STI(214) including the bird's beaks is formed by treating the CVD oxide layer with CMP(Chemical Mechanical Polishing) so that the nitride layer remaines on the pad oxide layer at the designated depth. The first and second active regions are exposed by removing the remaining nitride layer and pad oxide layer. After performing CMOS-well ion implantation and channel ion implantation, a nitride layer is formed on the first active region by deposition and etching thereof, while the second active region is exposed. The first thermal oxide layer(218) for one gate is formed on the second active region by using the nitride layer as a mask. Removing the nitride layer, the second thermal oxide layer(220) for another gate is formed on the first active region.
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