| 摘要 |
A method for forming a semiconductor device is provided to improve electrical properties and GOI(Gate Oxide Integrity) by forming a gate oxide layer with different thickness using a nitrogen ion-implantation process. An isolation layer(110) is formed in a substrate(100) for defining a cell transistor region(1000a), a high-voltage device region(1000b), a normal transistor region(1000c), and a low-voltage device region(1000d). Heavily doped nitrogen ions are implanted into the low-voltage device region. Lightly doped nitrogen ions are implanted into the normal transistor region. A first gate oxide layer is formed on the substrate. The resultant structure is wet-etched to remove entirely the gate oxide layer of the low-voltage device region by using a photoresist pattern to cover the cell transistor region. After the photoresist pattern is removed, a second gate oxide layer is formed on the resultant structure, thereby forming a stepped gate oxide layer(180a,180b,180c,180d) having different thickness according to the each region.
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