1 700 V trench IGBT with a design of strip-cells and dummy trench structure was developed based on the trench gate key processes in 8 inch fabrication. In dummy trench structure area, the effect of P-well interconnection types on IGBT’s static/ dynamic performance and safe operation area were studied by Silvaco simulation and substrate testing. Compared with the two P-well interconnection typeed, device with floating P-well showed lower conduction and switching losses, and wider RBSOA than that with ground P-well. The intrinsic mechanism which made the difference was analyzed. The device with floating P-well, field stop structure and carrier storage layer showed a decent comprehensive performance, and had passed necessary qualification before release.