Enhancing selectivity during formation of a channel semiconductor alloy by a wet oxidation process

A method of forming a semiconductor device, the method comprising:

• forming a silicon oxide layer on a first active region and a second active region by performing an oxidation process, said first and second active regions being delineated by an isolation structure, a thickness variation of said silicon oxide layer in said first and second active regions being approximately 20 percent or less;
• removing said silicon oxide layer selectively from above said first active region;
• forming a threshold adjusting semiconductor material in said first active region and using said silicon oxide layer formed on said second active region as a deposition mask, performing a cleaning process prior to forming said threshold adjusting semiconductor material and after selectively removing said silicon oxide layer from said second active region, wherein said cleaning process reduces a thickness of said silicon oxide layer;
• removing said silicon oxide layer from above said second active region;
• and
• forming a first gate electrode structure of a first transistor on said threshold adjusting semiconductor material and a second gate electrode structure of a second transistor on said second active region.