Due to further optimization of the semiconductor devices towards lower on-state resistance RON the net doping concentration of the drift region 153 of modern devices is increased. Simulations revealed that the breakdown location in case of a higher doping concentration of the drift region 153 may move to the end of the last spicular trench in the edge termination area as shown in FIG. 4A. FIG. 4A illustrates the distribution of the electrical field strength under blocking conditions, i.e. when no conductive channel is formed and a high voltage difference appears between source region and drain region. The large voltage drop between source region and drain region must be accommodated by the drift region. The electrical field strength occurring in the drift region can be large.
The simulation of the distribution of the electrical field strength in FIG. 4A shows that high field strength appears along the last spicular trench which is the leftmost spicular trench in FIGS. 4A and 4B. FIG. 4B illustrates the distribution of the electrostatic potential under blocking condition. The distribution of the electrostatic potential in FIG. 4B indicates that the potential changes vary rapidly at the outer region of the last spicular trench, resulting in high electric field strength. To improve the blocking capability of the edge termination area, it is desired to relax the electrostatic potential distribution at the end of the termination structure.
