Method of forming shaped source/drain epitaxial layers of a semiconductor device

A semiconductor device, comprising:

• a fin structure disposed on a substrate, the fin structure protruding from the substrate in a first direction and extending in a second direction perpendicular to the first direction;
• an isolation insulating layer disposed over the fin structure, wherein a first portion of the fin structure is exposed from the isolation insulating layer and a second portion of the fin structure is embedded in the isolation insulating layer;
• a gate structure disposed over a part of the first portion of the fin structure;
• a source/drain (SD) epitaxial structure disposed on opposite sides of the gate structure in an S/D region;
• and
• a dielectric layer disposed over sidewalls of the first portion of the fin structure in the S/D region not covered by the gate structure, wherein the dielectric layer extends an entire length of the S/D region in the second direction, wherein the dielectric layer covers the sidewalls of the first portion of the fin structure in a region of the SD epitaxial structure, wherein the dielectric layer that covers the sidewalls of the first portion of the fin structure in the region of the SD epitaxial structure is asymmetric, and wherein the SD epitaxial structure formed over the dielectric layer that covers the first portion of the fin structure in the region of the SD epitaxial structure is asymmetric.

A semiconductor device, comprising:

• a first structure including a fin made of a first material disposed on a substrate, the first structure extends in a first direction, the first structure comprises a first portion exposed and a second portion embedded;
• a gate structure disposed over a part of the first portion of the fin;
• a dielectric layer disposed over sidewalls of the first portion of the fin in a source/drain region not covered by the gate structure, wherein the dielectric layer extends an entire length of the source/drain region in the first direction;
• and
• a source/drain (SD) epitaxial structure disposed in the source/drain region, wherein a top part of the SD epitaxial structure includes flat side surfaces perpendicular to the first direction, wherein the dielectric layer covers the sidewalls of the first portion of the fin in a region of the SD epitaxial structure, wherein the dielectric layer that covers the sidewalls of the first portion of the fin in the source/drain region is asymmetric, and wherein the SD epitaxial structure formed over the dielectric layer that covers the first portion of the fin in the region of the SD epitaxial structure is asymmetric.