An image sensor and a method for manufacturing the same are provided. In the method, a photoresist is formed on a substrate including a photodiode region and a gate electrode opposite to the photodiode region on the basis of the gate electrode. An oxide layer is formed to a specific thickness on both the photodiode region and a part of the gate electrode. The photoresist is removed from the substrate and cleaned. A first oxide film is formed on the substrate, the gate electrode, and the oxide layer remaining on the photodiode region. A nitride film is formed on the first oxide film. And a second oxide film is formed on the nitride film. Blank etching is performed on the first oxide film, the nitride film, and the second oxide film to form a spacer at the side of the gate electrode.