Patent ID: 7816744

Claim:
A semiconductor structure comprising: a semiconductor substrate; a first well region of a first conductivity type overlying the semiconductor substrate; a second well region of a second conductivity type opposite the first conductivity type overlying the semiconductor substrate and laterally adjoining the first well region; a gate dielectric over the first well region and the second well region; a gate electrode on the gate dielectric, wherein the gate electrode comprises a first portion over the second well region, a second portion over the first well region, and wherein the first portion has a first impurity concentration lower than a second impurity concentration of the second portion; and an insulation region in a recess of the second well region, wherein the gate electrode has an edge directly over the insulation region and an inner edge of the recess is directly under the gate electrode, wherein the first and the second portions of the gate electrode have a first interface horizontally between the inner edge of the recess and a second interface, wherein the second interface is an interface of the first and the second well regions.