| 摘要 |
A semiconductor device structure with differential field oxide thicknesses. A single field oxidation step produces a nitrided field oxide region (322) that is thinner than a non-nitrided field oxide region (324). The bird's beak (326) of the nitrided field oxide (322) encroaches less into the active cell region than the bird's beak (328) of the thicker non-nitrided field oxide (324). The differential field oxide thicknesses allow isolation of multi-voltage integrated circuit devices, such as flash memory devices, while increasing available active cell area for a given design rule.
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