Single transistor-based oscillator, which has a floating body, is realized by employing single transistor latch (STL) phenomenon that induces inherent oscillatory behavior from iterative charging and discharging process. Since the STL is a sensitive phenomenon on the temperature, oscillation frequency changes at different temperature. From quantitative analysis on the temperature dependent oscillatory behavior, oscillation mechanism is studied and temperature sensor application is proposed. Compared to a circuit-based ring oscillator temperature sensor, single transistor-based oscillator temperature sensor requires smaller area, lower hardware cost, and lower power consumption. These features are advantageous for IoT and SoC applications.