Seal ring structures are provided with rounded corner junctions or corner junctions that include polygons. The seal rings surround generally rectangular semiconductor devices such as integrated circuits, image sensors and other devices. The seal ring includes a configuration of two sets of generally parallel opposed sides and the corner junctions are the junctions at which adjacent orthogonal seal ring sides are joined. The seal rings are trench structures or filled trench structures in various embodiments. The rounded corner junctions are formed by a curved arc or multiple line segments joined together at various angles. The corner junctions that include one or more enclosed polygons include polygons with at least one polygon side being formed by one of the seal ring sides.