Semiconductor device and method for fabricating the same

A semiconductor device includes a device isolation layer on a semiconductor substrate defining an active region in the semiconductor substrate, a low voltage well of a first conductivity type in the active region of the semiconductor substrate, a high voltage impurity region of a second conductivity type in the active region of the semiconductor substrate, the high voltage impurity region positioned in an upper portion of the low voltage well, a high concentration impurity region of the second conductivity type within the high voltage impurity region and spaced apart from the device isolation layer, and a floating impurity region of the first conductivity type between the device isolation layer and the high concentration impurity region, the floating impurity region being a portion of an upper surface of the active region.