For a power semiconductor device, usually widely used as a switch or rectifier in power supply applications, one of its particularly important requirements relates to the characteristic of breakdown voltage to endure high voltage. As devices in such applications evolve, a great deal of efforts has been paid to boast the breakdown voltage. The fruit of such efforts is an IGBT, gradually gaining wider applications for modern devices and appliances due to its various advantages. The IGBT is an element combining advantages of MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) structure as well as advantages of BJT (Bipolar Junction Transistor) structure. Combined with fast switching characteristic of the MOSFET along with high-current and low-saturation-voltage capability of the BJT, the IGBT expands its scope of applications such as display, automobile, motor and household appliances. Breakdown voltage under the high voltage environment is a key characteristic required in the IGBT, which is therefore designed by implementing an edge-termination structure — called edge termination region — in the lateral side of its junction so as to alleviate the electric field in the junction edge.