An overlay mark comprises a first feature in a first layer. The first feature has a length extending in a first longitudinal direction and a width extending in a second longitudinal direction. The length of the first feature is greater than the width of the first feature. The overlay mark also comprises a second feature in a second layer over the first layer. The second feature has a length extending in the second longitudinal direction and a width extending in the first longitudinal direction. The length of the second feature is greater than the width of the second feature. The overlay mark further comprises a third feature in a third layer over the second layer. The third feature is a box-shaped opening in the third layer.