An ultra-high voltage device is provided. The ultra-high voltage device includes a substrate, a first well zone formed in the substrate, a second well zone having a surface formed in the substrate adjacent to the first well zone, a gate oxide formed on the first well zone and the second well zone of the substrate, a gate formed on the gate oxide, a channel formed in the first well zone underneath the gate oxide, an accumulation region formed in the second well zone underneath the gate oxide adjacent to the channel, wherein only a part of the accumulation region is implanted with a dopant to form an implant region therein, and an insulation region formed on the surface of the second well zone of the substrate adjacent to the accumulation region, wherein a boundary is formed between the insulation region and the accumulation region.