angstroms advantageously the upper source stressor recess 321 and the upper drain stressor recess 322 each have substantially planar basal surfaces 321 a 322 a respectively advantageously the upper source stressor recess 321 and the upper drain stressor recess 322 are formed by a step of anisotropic reactive ion etching fig3 c shows the structure of fig3 b following epitaxial growth of a second semiconductor material in the upper source stressor recess 321 and the upper drain stressor recess 322 an epitaxy preclean of the exposed surfaces of the substrate is performed prior to selective epitaxial growth so that growth of high quality epitaxial material may take place advantageously the epitaxy preclean is performed using hf either in a gaseous or liquid solution form or by a combination of steps and chemicals that include hf in a gaseous or liquid form prior to selective epitaxial growth a pre bake step may also be performed to ensure good quality epitaxial layers are formed the pre bake step may include the steps of heating to a temperature in the range of about 750 u00b0 c to about 1000 u00b0 c for a duration in the range of about 2 seconds to about 20 minutes advantageously the pre bake step is performed in a temperature range of about 750 u00b0 c to.