| 摘要 |
A CMOS transistor is fasbricated by forming the n-wells with both phosphorus and arsenic implants. The arsenic, with its lower diffusion coefficient, tends to concentrate near the top surface of the n-wells, with the phosphorus penetrating sufficiently to define the n-wells at the desired depth. A boron channel stop implant is later applied without masking over the n-wells. Since the arsenic implant is concentrated near the surface, the arsenic impurities overcome the effects of the boron impurities. Additional boron required for n-channel channel stop is provided by n-channel transistor punch-through implantation.
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