An image sensor capable of reducing noises includes a pixel array, a control circuit and a correlation double sampling (CDS) circuit array. The CDS circuit array is coupled between the pixel array and the control circuit, and includes a plurality of CDS circuit units, of which each CDS circuit unit includes a silicon substrate, a MOS device formed on the silicon substrate and connected to a voltage floating node of the CDS circuit unit, and a plurality of metal layers placed on the MOS device for providing electrical connection for the CDS circuit unit and for blocking light illumination on the MOS device.