A device includes a crystalline material within an area confined by an insulator. A surface of the crystalline material has a reduced roughness. One example includes obtaining a surface with reduced roughness by using a planarization process configured with a selectivity of the crystalline material to the insulator greater than one. In a preferred embodiment, the planarization process uses a composition including abrasive spherical silica, H2O2 and water. In a preferred embodiment, the area confined by the insulator is an opening in the insulator having an aspect ratio sufficient to trap defects using an ART technique.