Method of increasing the depth of lightly doping in a high voltage device

Abstract

A method for fabricating a high vltage device with double diffusion structure provides a pad oxide layer on a silicon substrate. A silicon nitride layer is formed and patterned to expose isolation regions. A first mask covers the partial isolation regions spaced from the silicon nitride layer. A well region is formed underlay the silicon nitride layer. A second mask covers the partial isolation region spaced from the silicon nitride layer and the partial silicon nitride layer. First doped regions are formed underlay the partial silicon nitride layer. Then the isolation regions are formed partially on the first doped regions. Next, a third mask covers the pad oxide layer and the partial isolation regions and second doped regions are formed spaced from the first doped regions and below the isolation regions. A gate is formed and located between the first doped regions and a spacer on a side-wall thereof. Third doped regions are formed in the first doped regions.