Semiconductor device structure and methods of forming the same

A method, comprising:

• forming a first source/drain region over a substrate;
• forming a contact etch stop layer around the first source/drain region;
• forming an interlayer dielectric layer on the contact etch stop layer;
• forming a first opening in the interlayer dielectric layer, wherein a first portion of the contact etch stop layer is exposed and is a part of a sidewall defining the first opening;
• removing the exposed first portion of the contact etch stop layer to form a second opening, wherein a portion of a side surface of the first source/drain region is exposed in the second opening;
• and
• forming a first conductive feature in the first and second openings.

A method, comprising:

• forming a first source/drain region over a substrate;
• forming a dielectric material over the first source/drain region;
• forming a second source/drain region over the dielectric material;
• removing portions of the dielectric material, wherein a side surface of a remaining portion of the dielectric material has a concave profile;
• forming a contact etch stop layer around the first source/drain region and the second source/drain region;
• forming an interlayer dielectric layer on the contact etch stop layer;
• forming an opening in the interlayer dielectric layer and the contact etch stop layer, wherein a portion of a side surface of the second source/drain region is exposed;
• and
• forming a conductive feature in the opening.