An IR sensing transistor according to an exemplary embodiment of the present invention includes: a light blocking layer formed on a substrate; a gate insulating layer formed on the light blocking layer; a semiconductor formed on the gate insulating layer; a pair of ohmic contact members formed on the semiconductor; a source electrode and a drain electrode formed on respective ones of the ohmic contact members; a passivation layer formed on the source electrode and the drain electrode; and a gate electrode formed on the passivation layer, wherein substantially all of the gate insulating layer lies on the light blocking layer.