Back-side implantation and nanosecond laser annealing for source/drain regions

A method, comprising:

• forming a plurality of epitaxial structures on opposite sides of a semiconductive nanostructure;
• forming a gate structure wrapping around the semiconductive nanostructure and between the epitaxial structures;
• forming a first metal silicide layer on a front-side surface of one of the epitaxial structures;
• after forming first metal silicide layer, forming an amorphous region extending from a back-side surface of the one of the epitaxial structures toward the front-side surface of the one of the epitaxial structures;
• performing a nanosecond laser annealing (NSA) process on the amorphous region from the back-side surface of the one of the epitaxial structures, wherein the NSA process recrystallizes the amorphous region;
• performing a metal silicidation process on the thinned amorphous region, such that the thinned amorphous region is converted to a second metal silicide layer;
• and
• forming a metal contact over the second metal silicide layer.

A method, comprising:

• forming a first metal silicide layer on a front-side of a top-tier epitaxial source/drain region of a top-tier transistor;
• implanting a dopant into a bottom-tier epitaxial source/drain region of a bottom-tier transistor located below the top-tier transistor, from a back-side of the bottom-tier epitaxial source/drain region;
• performing a multi-shot nanosecond laser annealing (NSA) process on the bottom-tier epitaxial source/drain region from the back-side of the bottom-tier epitaxial source/drain region, wherein the multi-shot NSA process uses a laser with a wavelength of less than about 400 nm;
• forming a second metal silicide layer on the back-side of the bottom-tier epitaxial source/drain region;
• and
• forming a metal contact over the second metal silicide layer.