Device having a laterally graded well structure and a method for its manufacture

Provided are a device and method for its manufacture. In one example, the device includes a semiconductor substrate that includes a well region formed using a first-type dopant. First and second doped regions are formed in the well region using a second-type dopant, and the first and second doped regions are separated from each other by a dielectric isolation feature. A third doped region is formed in the well region using the first-type dopant and positioned under the dielectric isolation feature and between the first doped region and the second doped region. The third doped region has a dopant concentration higher than that of the well region.