Patent ID: 8754476

Claim:
A high voltage device, which is formed in a first conductive type substrate, the substrate having a second conductive type well and a device region defined by at least one isolation region in the well, the high voltage device comprising: a field oxide region, which is formed in the device region; a gate, which is formed in the device region on a surface of the substrate, and part of the gate is located above the field oxide region such that the field oxide region has one boundary side beneath the gate; a second conductive type source, and a second conductive type drain, which are formed at two sides of the gate in the device region respectively, and the drain and the source are separated by the gate and the field oxide region from top view; and a first low concentration doped region having a second conductive type, which is formed beneath the gate and has a second conductive type impurity concentration which is lower than that of the well, wherein from top view, the first low concentration doped region has an area within the gate and not larger than an area of the gate, and the first low concentration doped region has a depth which is deeper than that of the source and drain, and wherein the first low concentration doped region surrounds the one boundary side of the field oxide region so that a part of the first low concentration doped region is located beneath the field oxide region and another part of the first low concentration doped region is located outside the field oxide region.