An ESD device includes a first and second well regions disposed in a semiconductor substrate. The first well region comprises a plurality of N wells spaced at a predetermined length. A heavily doped P+ region and a heavily doped N+ region are disposed in each of the N wells. The heavily doped N+ region is coupled to Vdd and a heavily doped P+ region in an N well is electrically coupled to the heavily doped N+ region in an adjacent N well. The second well region comprises a P well abutting an N well. A heavily doped P+ region and a heavily doped N+ region are disposed in the P well. The heavily doped N+ region in the P well is electrically coupled to the heavily doped P+ region of the adjacent N well in common with an I/O circuit, and the heavily doped P+ region is coupled to Vss.