Diamond is a hopeful candidate for power switching device which can operate at high temperature as a “Cooling system free” device, yet at a high current. Recently we have developed a 3D diamond CVD growth method coupled with a sophisticated “direct wafer fabrication technique” to fabricate diamond wafer without slicing. Currently, half inch size single crystal diamond substrates are available for R&D of diamond device. Using this technique, we have increased the device fabrication size from 3x3mm2 to half inch wafer. In this paper, we present the results of measurements on the first device fabricated on a half inch size CVD substrate. We have carried out the first device characteristics mapping for diamond, and have observed the influence of substrate characteristics on the SBD characteristics.