Diffusion layer for semiconductor devices

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

• forming a gate electrode on a substrate;
• recessing source/drain regions of the gate electrode;
• forming a barrier layer in the substrate in the source/drain regions;
• forming a first semiconductor layer in the source/drain regions;
• and
• forming a semiconductor alloy layer on the first semiconductor layer.

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

• providing a substrate;
• forming a gate electrode on the substrate;
• forming dummy spacers along opposing sides of the gate electrode;
• recessing the substrate adjacent the dummy spacers, thereby forming recessed regions;
• forming a barrier layer in the recessed regions of the substrate;
• forming a first semiconductor layer in the recessed regions;
• and
• forming a second semiconductor layer on the first semiconductor layer, the second semiconductor layer having a different lattice structure than the first semiconductor layer.