| 摘要 |
PURPOSE: To improve the flatness of a device by oxidizing a silicon substrate coated with the first and second parts of an oxide layer, having first and second surface areas grown on the silicon substrate. CONSTITUTION: After an oxide layer 4 is grown on a silicon wafer substrate 2, a silicon nitride layer 6 is formed on the layer 4 and etched after the layer 6 is patterned by using a photoresist layer 8. Then an area 10 for limiting a well to be formed next is exposed, and a P-type dopant 12 is injected into the area 10. After removing the photoresist layer 8, an oxide mask 14 is grown on the injected layer 12 in the area 10, and the silicon nitride layer 6 is removed. After removing the layer 6, a dopant 18 of conductivity opposite to that of the dopant 12 is injected so as to surround the area 10. Then the substrate 2 is oxidized, so as to drive the injected materials by oxidation and to reduce a level difference 20 between the oxide mask 14 and the remaining part of the original oxide layer 4, and all oxide layers are removed. Therefore, the flatness of a device can be improved.
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