Patent ID: 7214591

Claim:
A method for fabricating a high-voltage metal-oxide-semiconductor (HV-MOS) device, comprising: forming a patterned first mask layer on a substrate, having a first part covering a channel region in the substrate and two second parts beside the first part covering two regions of the substrate predetermined for a source and a drain, respectively, wherein the first part is apart from at least one of the two second parts; forming a patterned second mask layer over the substrate, having an opening therein exposing the substrate between the first part and the at least one second part of the first mask layer and exposing another portion of the substrate at periphery of the at least one second part of the first mask layer, wherein at least part of the patterned second mask layer is formed directly on the substrate away from the periphery of the at least one second part of the first mask layer; implanting a dopant into the substrate using the first and second mask layers as a mask to form doped regions in the exposed portions of the substrate; removing the second mask layer; forming a field isolation layer on the substrate using the first mask layer as a mask, while the doped region under the field isolation layer between the first part and the at least one second part of the first mask layer serves as a drift region, and the doped region under the field isolation layer at the periphery of the at least one second part of the first mask layer serves as a modifying doped region; removing the first mask layer; forming a gate dielectric layer and a gate covering the channel region; and forming a source region and a drain region in the substrate beside the gate using the gate and the field isolation layer as a mask.