An overlay mark includes a first feature of a plurality of first alignment segments extending along a first direction in a first layer, a second feature of a plurality of second alignment segments extending along a second direction in a second layer over the first layer, and a third feature of a plurality of third alignment segments extending along the first direction and a plurality of fourth alignment segments extending along the second direction in a third layer over the second layer. In a plan view, each first alignment segment of the plurality of first alignment segments is adjacent to a corresponding third alignment segment of the plurality of third alignment segments along the first direction, and each second alignment segment of the plurality of second alignment segments is adjacent to a corresponding forth alignment segment of the plurality of fourth alignment segments along the second direction.