Epitaxial features for multi-gate devices and fabrication methods thereof

A method of manufacturing a semiconductor device, comprising:

• patterning a substrate to form a fin, the fin having a first source/drain region, a second source/drain region, and a channel region between the first and second source/drain regions;
• forming a gate stack over the channel region of the fin;
• forming a cover structure having a first portion aside the gate stack and a second portion extending parallel to the gate stack and across the first source/drain region in a top view of the semiconductor device;
• recessing the first and second source/drain regions of the fin to form a first trench and a second trench in the first source/drain region and at least a third trench in the second source/drain region in a cross-sectional view of the semiconductor device cut along the fin;
• and
• epitaxially growing a first epitaxial feature from the first trench, a second epitaxial feature from the second trench, and a third epitaxial feature from the third trench, wherein the first and second epitaxial features merge above a top surface of the fin.

A semiconductor device, comprising:

• a substrate;
• a plurality of fins protruding from the substrate, each of the fins extending lengthwise in a first direction;
• a gate stack disposed over the fins, the gate stack extending lengthwise in a second direction perpendicular to the first direction;
• a first epitaxial feature disposed on a first side of the gate stack;
• and
• a second epitaxial feature disposed on a second side of the gate stack,
• wherein:
• the first epitaxial feature extends continuously such that each of the fins is directly under the first epitaxial feature, and
• in a cross-sectional view of the semiconductor device cut along one of the fins, the first epitaxial feature includes a first lower portion extending below a top surface of the one of the fins, a second lower portion extending below the top surface of the one of the fins, and a connecting portion adjoining the first and second lower portions above the top surface of the one of the fins.