Method for forming semiconductor structure

A method for forming a semiconductor structure, comprising:

• forming a plurality of nanostructures over a fin element;
• forming a source/drain feature adjoining the plurality of nanostructures;
• forming an interlayer dielectric layer over the source/drain feature;
• etching the interlayer dielectric layer to form an opening;
• implanting a dopant through a first side surface of the interlayer dielectric layer exposed from the opening into the interlayer dielectric layer;
• forming a contact liner along sidewalls of the opening;
• and
• forming a contact plug nested within the contact liner.

A method for forming a semiconductor structure, comprising:

• forming an active region over a substrate;
• forming a source/drain feature over a source/drain region of the active region;
• forming a gate stack over a channel region of the active region;
• forming a contact etching stop layer to cover the source/drain feature;
• forming an interlayer dielectric layer over the contact etching stop layer;
• etching the interlayer dielectric layer and the contact etching stop layer to form an opening;
• forming a dielectric layer in the opening, wherein the dielectric layer includes a first portion formed along a first sidewall of the opening and a second portion formed along a second sidewall of the opening;
• treating the first portion of the dielectric layer with ion beams;
• etching the dielectric layer, wherein the first portion of the dielectric layer is etched by a first etching rate, and the second portion of the dielectric layer is etched by a second etching rate that is less than the first etching rate;
• and
• forming a contact plug in the opening.