How LDD (lightly doped drain) can lower the electric field?

[uney]

thanks a lot!

 

[uart]

- The blocking voltage of a mosfet is largely due to a reverse biased pn junction formed between the drain and the body or substrate.

- The voltage at a reverse biased junction is blocked by depletion regions that extend further into the least heavily doped side of the juntion. So the depletion region will be longer, and extend further into the drain, if the drain is lightly doped.

- The longer is the depletion region then the lower is the electric field strength in that region, for a given blocking voltage. Hence a LDD mosfet can block higher voltages but as a trade off would typically have higher on resistance an less current carrying capability.