In this paper, we report the performance of a novel photo-detector fabricated on an SOI substrate using a standard DTMOS process. The photo-detector is formed by connecting the NMOSFET gate and body. The gate-body terminal is left floating so that the potential can be modulated by illumination. The depletion region induced by the floating gate separates the optically generated electron-hole pairs in the direction perpendicular to the current. This increases the body potential and induces positive charges to the gate due to the gate/body tie. It results in further turn on of the NMOSFET and extra optical current. A wide signal range of more than six orders of magnitude and a maximum responsivity of 1.2 x 10(3) A/W have been obtained with an operating voltage as low as 0.2 V. The behavior of the device under scaling is also discussed.