Ultra-high voltage devices and method for fabricating the same

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 formed in the substrate adjacent to the first well zone, a gate oxide layer formed on the first well zone and the second well zone, a gate formed on the gate oxide layer, an insulation region formed on the surface of the second well zone, a first implant region formed in the second well zone underneath the insulation region, a second implant region formed below the first implant region, and a junction formed between the first implant region and the second implant region. At least one of the first implant region and the second implant region includes at least two sub-implant regions having different implant concentrations. The sub-implant region having the higher implant concentration is adjacent to the junction.