Method for fabricating metal oxide semiconductor

A method for forming a metal oxide semiconductor transistor, which method is performed on a substrate comprising a gate thereon, comprising the steps of:

• forming an offset spacer on the sidewall of the gate;
• forming an source/drain extension around the offset spacer after which is formed;
• forming an insulating spacer on the sidewall of the offset spacer;
• forming a source/drain region in the substrate, wherein the source/drain region comprises a part of the source/drain extension;
• removing the offset spacer;
• and
• forming a halo doped region in the substrate beside the source/drain region.

A method for forming a halo doped region, which method is performed on a substrate comprising at least a gate thereon, comprising the steps of:

• forming an offset spacer on the sidewall of the gate;
• forming a source/drain extension in the substrate around the offset spacer after the offset spacer is formed;
• forming an insulating spacer on the sidewall of the offset spacer;
• forming a source/drain region in the substrate wherein the source/drain region comprises a part of the source/drain extension;
• forming a salicide layer on the gate and the source/drain region;
• removing the offset spacer;
• and
• forming a halo doped region in the substrate beside source/drain region.