Abstract: High voltage semiconductor devices and methods for fabricating the same are provided. An exemplary embodiment of a semiconductor device capable of high-voltage operation, comprising a substrate comprising a first well formed therein. A gate stack is formed overlying the substrate, comprising a gate dielectric layer and a gate electrode formed thereon. A channel well and a second well are formed in portions of the first well. A source region is formed in a portion of the channel well. A drain region is formed in a portion of the second well, wherein the gate dielectric layer comprises a relatively thinner portion at one end of the gate stack adjacent to the source region and a relatively thicker portion at one end of the gate stack adjacent to and directly contacts the drain region.