Embodiments relate to an image sensor and a method for manufacturing an image sensor that may prevent a photoresist pattern from remaining on gates by forming a floating diffusion area faster than the gates. According to embodiments, since the gates may not be influenced by an ion implantation process, current characteristics and operation reliability may be enhanced. According to embodiments, the method may include forming dummy ion implantation mask patterns for forming a floating diffusion area over an epitaxial layer and forming an ion implantation mask pattern over the epitaxial layer and at least a portion of the dummy ion implantation mask patterns, so as to form the floating diffusion area by performing an ion implantation process.