According to the CMOS device on SOI substrate (SOI CMOS device), we investigate the influence of holes accumulated in buried oxide film (BOX) under the radiation environment by monitoring leakage current with back bias. We confirmed that the leakage current has the colleration to total ionizing dose (TID). SOI CMOS assumed to be not good on TID, compared to bulk. But, we confirmed the tolerance to TID in SOI CMOS was improved from 200 to 3000 Gy(Si) with the process optimization, which is better than bulk CMOS.