A semiconductor device with dummy and active pixel structures and a method of fabricating the same are disclosed. The semiconductor device includes a first pixel region with a first pixel structure, a second pixel region, surrounding the first pixel region, includes a second pixel structure adjacent to the first pixel structure and electrically isolated from the first pixel structure, and a contact pad region with a pad structure disposed adjacent to the second pixel region. The first pixel structure includes a first epitaxial structure disposed within a substrate and a first capping layer disposed on the first epitaxial structure. The second pixel structure includes a second epitaxial structure disposed within the substrate and a second capping layer disposed on the second epitaxial structure. Top surfaces of the first and second epitaxial structures are substantially coplanar with each other. The first and second epitaxial structures includes a same semiconductor material.