| 摘要 |
An N type buried layer is formed, in one embodiment, by a non selective implant on the surface of a wafer and later diffusion. Subsequently, the wafer is masked and a selective P type buried layer is formed by implant and diffusion. The coefficient of diffusion of the P type buried layer dopant is greater than the N type buried layer dopant so that connections can be made to the P type buried layer by P wells which have a lower dopant concentration than the N buried layer.
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