A semiconductor device includes a quantum dot and a plurality of layers, wherein said plurality of layers includes: a first layer; a stressor layer; and a patterned layer wherein said stressor layer overlies said first layer and said patterned layer overlies said stressor layer; wherein said stressor layer has a substantially different lattice constant to said first layer and said patterned layer and has a pit provided in said layer; said quantum dot lying above said patterned layer aligned with said pit.