Source/drain contact structure

A semiconductor device, comprising:

• a first interconnect structure comprising a passivation layer and a first power rail disposed in the passivation layer;
• an isolation feature disposed on the first interconnect structure;
• a first transistor over the isolation feature and comprising:
• first nanostructures, and
• a first source feature adjoining the first nanostructures along a first direction;
• a second transistor over the first transistor and comprising:
• second nanostructures, and
• a second source feature adjoining the second nanostructures along the first direction;
• a second interconnect structure over the second transistor;
• and
• a backside source contact extending from a top surface of the first power rail, through the isolation feature to electrically couple to the first source feature,
• wherein the backside source contact is directly below the first source feature,
• wherein the first source feature is sandwiched directly between a first hybrid fin and a second hybrid fin along a second direction perpendicular to the first direction,
• wherein the second source feature is coupled to a second power rail in the first interconnect structure.

A method, comprising:

• receiving a workpiece comprising a first substrate and a first stack over the first substrate, the first stack including a first plurality of channel layers interleaved by a first plurality of sacrificial layers;
• forming a first fin-shaped structure from the first stack and a portion of the first substrate, the first fin-shaped structure comprising a first source region and a first drain region;
• forming a first hybrid fin and a second hybrid fin that extend parallel to the first fin-shaped structure, the first hybrid fin comprising a first conductive feature embedded in a first dielectric feature and the second hybrid fin comprising a second conductive feature embedded in a second dielectric feature;
• forming a first source feature over the first source region and a first drain feature over the first drain region;
• forming a first source contact in direct contact with the first source feature and the first conductive feature;
• forming a first drain contact in direct contact with the first drain feature;
• depositing a capping layer over the first source contact and the first drain contact;
• bonding a second stack over the capping layer, the second stack including a second plurality of channel layers interleaved by a second plurality of sacrificial layers;
• forming a second fin-shaped structure from the second stack, the second fin-shaped structure comprising a second source region and a second drain region;
• forming a third hybrid fin and a fourth hybrid fin that extend parallel to the second fin-shaped structure, the third hybrid fin comprising a third conductive feature embedded in a third dielectric feature and the fourth hybrid fin comprising a fourth conductive feature embedded in a fourth dielectric feature;
• forming a second source feature over the second source region and a second drain feature over the second drain region;
• forming a second source contact in direct contact with the second source feature and the third conductive feature;
• and
• forming a second drain contact in direct contact with the second drain feature.