Method for fabricating contact electrode and semiconductor device

A method for fabricating at least one contact, comprising:

• forming at least one contact hole on a semiconductor device structure, the semiconductor device structure comprising a substrate, a gate, a source, and a drain, the bottom of the at least one contact hole exposing the source and/or the drain, wherein the source includes a source in-situ doped layer formed inside the substrate and a raised source layer on the source in-situ doped layer, and the drain includes a drain in-situ doped layer formed inside the substrate and a raised drain layer on the drain in-situ doped layer;
• etching the source in-situ doped layer and the raised source layer and/or the drain in-situ doped layer and the raised drain layer exposed at the bottom of the at least one contact hole, so as to form at least one contact hole having an enlarged bottom inside both the raised source layer and the source in-situ doped layer, and/or inside both the raised drain layer and the drain in-situ doped layer, wherein the enlarged bottom of the at least one contact has a diamondoid cross section;
• and
• filling the at least one contact hole having the enlarged bottom with a contact material to form at least one contact contacting with the source and/or the drain, so that the at least one contact has an enlarged end which is in contact with the source and/or the drain.