An image sensor device includes a semiconductor device, a plurality of photo sensitive regions, a dielectric layer, a grid structure, and a plurality of convex dielectric lenses. The plurality of photo sensitive regions are in the semiconductor substrate. The dielectric layer is on a backside surface of the semiconductor substrate facing away from the plurality of photo sensitive regions. The grid structure is on a backside surface of the dielectric layer facing away from the semiconductor substrate. The grid structure includes a plurality of grid lines spaced from each other. The plurality of convex dielectric lenses are alternately arranged with the plurality of grid lines of the grid structure on the backside surface of the dielectric layer. Apexes of the plurality of convex dielectric lenses are lower than top ends of the plurality of grid lines of the grid structure.