In this paper, we report high-temperature (up to 573 K) device characteristics, such as subthreshold characteristics, threshold voltage, on-resistance, breakdown characteristics, breakdown voltage, and leakage current, for the thin-film silicon-on-insulator power MOSFETs based on experimental results. The subthreshold slope, on-resistance, and leakage current increase with increasing temperature. The breakdown voltage and threshold voltage decrease with increasing temperature. Dependences of these characteristics on the channel and drift lengths are also analyzed.