An electrostatic discharge (ESD) protection circuit structure includes a dual directional silicon controlled rectifier (SCR) formed in a substrate. The SCR includes first and second P-wells laterally interposed by an N-well. A deep N-well is disposed underneath the P-wells and the N-well. First and second N-type regions are disposed in the first and second P-wells, respectively, and are coupled to a pair of pads. First and second P-type regions are disposed in the first and second P-wells, respectively, are coupled to the pads, and are disposed closer to the N-well than the first and second N-type regions, respectively.