Contacts for highly scaled transistors

A semiconductor structure, comprising:

• a substrate;
• a isolation structure over the substrate
• a first fin structure extending from the substrate and rising above the isolation structure;
• a second fin structure extending from the substrate and rising above the isolation structure;
• a first source/drain feature disposed directly over the first fin structure;
• a second source/drain feature disposed directly over the second fin structure;
• a semiconductor-metal alloy layer disposed directly on surfaces of the first source/drain feature and surfaces of the second source/drain feature;
• a dielectric layer over the isolation structure, the first source/drain feature and the second source/drain feature;
• and
• a contact feature extending through the dielectric layer and in contact with the semiconductor-metal alloy layer,
• wherein the dielectric layer is in direct contact with the semiconductor-metal alloy layer.

A semiconductor structure, comprising:

• a substrate;
• a first fin structure and a second fin structure extending vertically from the substrate and lengthwise along a direction;
• a first source/drain feature disposed on the first fin structure, the first source/drain feature comprising two upwardly facing surfaces and two downwardly facing surfaces;
• a second source/drain feature disposed on the second fin structure, the second source/drain feature comprising two upwardly facing surfaces and two downwardly facing surfaces;
• a first contact layer over and in direct contact with the two upwardly facing surfaces and the two downwardly facing surfaces of the first source/drain feature;
• a second contact layer over and in direct contact with the two upwardly facing surfaces and the two downwardly facing surfaces of the second source/drain feature;
• a contact feature disposed over and in contact with the first contact layer and the second contact layer;
• and
• a dielectric layer disposed along sidewalls of the contact feature,
• wherein the dielectric layer is in direct contact with the first fin structure, the first contact layer, the second fin structure, and the second contact layer.