© Copyright owned by the author(s). Technology computer-aided design (TCAD), used in the semiconductor industry, simulates the semiconductor manufacturing process and the resulting device performance. We have used a device simulator to develop a highly radiation-tolerant n-in-p silicon strip and pixel sensors, both of which can operate at a very high voltage of up to 1000 V. We analyzed the electric field in the p-stop structures, novel punch-through-protection (PTP) structures, breakdown in the edge region, etc. and compared the analysis results with the measurement results of test structures; our findings contributed to the development of guiding principles for optimizing the critical structures. The TCAD device simulator is a valuable and effective tool as long as relevant semiconductor physics models and their parameters are implemented. We have yet to understand the modeling of the surface-bulk interplay after proton irradiation, the leakage current generation in the dicing edge, and other phenomena.