Embodiments of the disclosure provide an image sensor device. The image sensor device includes a semiconductor substrate. The semiconductor substrate has a front surface, a back surface opposite to the front surface, a light-sensing region close to the front surface, and a trench adjacent to the light-sensing region. The image sensor device includes a reflective layer positioned on an inner wall of the trench, wherein the reflective layer has a light reflectivity ranging from about 70% to about 100%.