An image sensor includes a substrate having a first surface and a second surface. The substrate includes a photo-sensitive region and a connection region. The image sensor also includes a buffer layer formed on the first surface of the substrate in the photo-sensitive region, and a metal grid formed on the buffer layer and including a plurality of staggered metal wires. The metal grid is connected to an operation voltage, and a plurality of trenches are formed in the metal grid with each trench surrounded by the metal wires. The image sensor further includes a plurality of color filters formed in the plurality of trenches of the metal grid. The metal grid induces charges in the substrate to prevent recombination between the charges generated by photo-sensitive components and the defects in the substrate. As such, the dark current is reduced, and the performance of the image sensor is improved.