A unit pixel formed on a substrate and configured to convert incident light to an electrical signal is provided. The unit pixel includes: a source having a source voltage supplied thereto and having a silicide layer for metal contact formed thereabove; a drain spaced apart from the source and having a silicide layer for metal contact formed thereabove; a channel formed between the source and the drain and having a current flowed therethrough; an insulating layer formed above the channel; and a floating gate having a nonsal structure in which no silicide layer is formed thereabove in order to facilitate an absorption of light, formed above the insulating layer so as to be placed between the source and the drain, and configured to control an amount of current flowing through the channel by an electric field generated by electron-hole pairs generated by the incident light. A body of the unit pixel is floated, and the electric field is configured to act on the channel by electrons aggregated toward the source and holes aggregated toward the drain by the source voltage supplied to the source.