A new method for fabricating semiconductor quantum rings has been developed. Instead ofusing the conventional GaAs cap layer, we used the GaAs/AlAs cap layer for the ringformation. The additional AlAs layer impedes the inward diffusion of the Ga and Al atomsand results in nicely formed ring structures with a more relaxed growth condition.Because of this layer, the ring-shaped structure can be maintained with a higherannealing temperature without being washed out by the intermixing of Ga/Al withIn in the central region of the dots. The shape and the strain distribution ofquantum rings have also been characterized by transmission electron microscopy.