A semiconductor structure. The structure includes (a) substrate, (b) a first semiconductor region on top of the substrate, wherein the first semiconductor region comprises a first semiconductor material and a second semiconductor material, which is different from the first semiconductor material, and wherein the first semiconductor region has a first crystallographic orientation, and (c) a third semiconductor region on top of the substrate which comprises the first and second semiconductor materials and has a second crystallographic orientation. The structure further includes a second semiconductor region and a fourth semiconductor region on top of the first and the third semiconductor regions respectively. Both second and fourth semiconductor regions comprise the first and second semiconductor materials. The second semiconductor region has the first crystallographic orientation, whereas the fourth semiconductor region has the second crystallographic orientation.