The breakdown characteristics of 4H-SiC p-n diode using Internal Ring(IR) termination technique are presented. N.-type 4H-SiC wafer having a 10um epilayer with a doping concentration of 5.4X10(15)/cm(3) is used to fabricate the p-n diode with a single or two IRs. IR is formed by boron implantation of single energy (360keV) with 5X10(14)/cm(2) dose and by activation annealing at 1700degreesC for 30min in Ar ambient. The breakdown voltage of the IR terminated device depends on the distance between the main junction and 1(st) ring. A p-n diode with two IRs termination structure exhibits a high breakdown voltage of 1812V. Due to the IRs, the peak electric field at the interface between SiC and the surface oxide is lower than that at the edge of the 2(nd) IR, which means that the breakdown of the device occurs at the edge of the 2(nd) IR. Therefore the IR structure is attractive planar termination technique for obtaining a high breakdown voltage of 4H-SiC power devices.