Abstract: For 3 300 V high voltage IGBT device, due to extremely high resistance of substrate, among those enhancing breakdown voltage terminal solution such as floating field ring, field plate, floating field ring plus field plate, JTE, VLD and floating field rings plus multistep field plates, floating field rings plus multistep field plates is the most feasible one. Based on the existing planar 3 300 V field stop (FS)IGBT platform, adopting floating field rings plus multistep field plates' terminal structure, the TCAD simulation shows that the breakdown voltage increases while the thickness of field plate increase. This TCAD simulation scheme is fabricated in process through the field plate thickness DOE (Design of Experiment), 3 300 V breakdown voltage is achieved. But as the thickness increase, the bow also increases accordingly, so the frontside and backside film deposition reflow optimization is carried out, the bow reduces significantly, which has weak relation with the thickness, meets the design requirement. The measured breakdown voltage result verified the TCAD simulation.