An image sensor device includes a substrate having a pixel array region, isolation structures in the substrate separating pixel regions from one another in the pixel array region, a photo-sensing region in each of the pixel regions, and a reflective cavity structure in the substrate within each of the pixel region. The reflective cavity structure continuously extends from a bottom of the isolation structure to a deeper central portion of each of the pixel regions, thereby forming a dish-like profile. The reflective cavity structure has a reflective index smaller than that of the substrate.