An n-type strained silicon MOSFET utilizes a strained silicon channel region formed on a silicon germanium substrate. Silicon regions are provided in the silicon geranium layer at opposing sides of the strained silicon channel region, and shallow source and drain extensions are implanted in the silicon regions. By forming the shallow source and drain extensions in silicon regions rather than in silicon germanium, source and drain extension distortions caused by the enhanced diffusion rate of arsenic in silicon germanium are avoided.