| 摘要 |
PURPOSE: A method for fabricating a semiconductor device is provided to advantageously cope with high speed and improve the quality of a gate oxide layer by forming a gate oxide layer having different thickness in a high voltage device, a normal device and a low voltage device, respectively. CONSTITUTION: An isolation layer for defining an active region is formed on a semiconductor substrate(10) having a cell region, a high voltage device region, a normal device region and a low voltage device region. The first nitrogen ions are implanted into a portion of the semiconductor substrate reserved for the low voltage device region. The second nitrogen ions with a dose lower than that of the first nitrogen ions are implanted into a portion of the semiconductor substrate reserved for the normal device region. The semiconductor substrate is thermally oxidized to form the first gate oxide layer on the resultant structure. The first gate oxide layer is blanket-etched until the semiconductor substrate in the thinnest region of the gate oxide layer is exposed. The resultant structure is thermally oxidized again to form the second gate oxide layer.
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