To achieve a 50% worldwide reduction of CO2by the middle of this century, development of energy saving power device technology using wide bandgap materials is urgently needed. Diamond is receiving increasing attention as a next generation material for wide bandgap semiconductors owing to its extreme characteristics. Research studies investigating large wafers, low resistivity, and low dislocation have accelerated. This study targets the use of wafers for power electronics applications, and the required machining technologies for diamond, including wafer shaping, slicing, and surface finishing, are introduced.