The SCR-based ESD device has a 4-layered PNPN structure (NPN and PNP junction transistors) disposed in SOI having first and second device wells (N-well and P-well) abut forming a NP junction near a midline. First and second contact regions disposed in device wells are coupled to high and low power sources (I/O pad and ground). Internal isolation regions (shallower STI) extending partially not touching the bottom of surface substrate separate the first and second contact regions. A vertical gate is disposed over the NP junction or over a shallower STI which overlaps the junction and separate the second contact regions in x-direction. One or more horizontal gates separate the second contact regions in y-direction and guide the device wells underneath the shallower STI to outer edges to connect with the first contact regions for body contacts. A process for forming the device is also disclosed and is compatible with CMOS processes.