Method for Forming Source/Drain Contacts

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

• providing a structure that includes:
• a substrate;
• a first gate structure and a second gate structure over the substrate;
• a first source/drain (S/D) feature comprising n-type doped silicon adjacent to the first gate structure;
• a second S/D feature comprising silicon germanium (SiGe) adjacent to the second gate structure;
• and
• one or more dielectric layers over sidewalls of the first and second gate structures and over the first and second S/D features;
• etching the one or more dielectric layers to expose the first and second S/D features;
• forming a masking layer over the first S/D feature;
• implanting the second S/D feature with gallium (Ga) while the masking layer is over the first S/D feature, resulting in a gallium-containing implant layer over the second S/D feature;
• removing the masking layer;
• etching the first and second S/D features with an oxygen-atom-containing etchant, resulting in conversion of a top portion of the gallium-containing implant layer into a gallium oxide containing layer while a bottom portion of the gallium-containing implant layer remains over the second S/D feature;
• removing the gallium oxide containing layer;
• depositing a metal layer over the first S/D feature and the bottom portion of the gallium-containing implant layer over the second S/D feature;
• and
• annealing the first and second S/D features.

A semiconductor device comprising:

• an n-type FinFET region including:
• a first gate stack;
• a first gate spacer over sidewalls of the first gate stack;
• an n-type epitaxial feature in a source/drain (S/D) region of the n-type FinFET region;
• and
• a first metal silicide layer over the n-type epitaxial feature;
• and
• a p-type FinFET region including:
• a second gate stack;
• a second gate spacer over sidewalls of the second gate stack;
• a silicon germanium (SiGe) epitaxial feature in an S/D region of the p-type FinFET region, wherein a top portion of the SiGe epitaxial feature includes gallium;
• and
• a second metal silicide layer over the top portion of the SiGe epitaxial feature.