A unit pixel formed on a substrate and configured to convert incident light to an electrical signal to constitute an image sensor provided. A 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, a light receiving part placed in a light receiving region of the surface of the image sensor and having changes in electrical properties caused by incident light therein; and a floating gate formed above the insulating layer so as to be placed between the source and the drain, configured to be electrically connected with the light receiving part, and configured to control an amount of current flowing through the channel by an electric field generated by the changes in electrical properties.