Source/drain for gate-all-around devices

A method of forming long channel and short channel nanosheet devices on a substrate, comprising:

• forming at least two stacks of alternating sacrificial layers and semiconductor nanosheet layers on a substrate;
• forming a separate gate sidewall spacer and dummy gate structure across each of at least two of the at least two stacks of alternating sacrificial layers and semiconductor nanosheet layers;
• forming a separate amorphous source/drain fill on each of opposite sides of the at least two of the at least two stacks of alternating sacrificial layers and semiconductor nanosheet layers;
• forming a source/drain encapsulation layer on each of the amorphous source/drain fills;
• removing the at least two dummy gate structures;
• removing the sacrificial layers from the at least two of the at least two stacks of alternating sacrificial layers and semiconductor nanosheet layers;
• forming a gate dielectric layer on exposed portions of the semiconductor nanosheet layers of the at least two stacks of alternating sacrificial layers and semiconductor nanosheet layers;
• forming a protective capping layer on the gate dielectric layer;
• and
• subjecting the amorphous source/drain fills to a recrystallization treatment to cause a phase change from the amorphous state to a single crystal or poly-crystalline phase, wherein the semiconductor nanosheet layers of a first of the at least two of the at least two stacks form shorter device channels than the semiconductor nanosheet layers of a second of the at least two of the at least two stacks.