Semiconductor device and manufacturing method thereof

A method, comprising:

• forming a semiconductor fin protruding above a substrate;
• forming isolation structures on opposite sides of the semiconductor fin;
• forming a gate structure crossing the semiconductor fin;
• forming a gate spacer along a sidewall of the gate structure;
• forming an interlayer dielectric (ILD) layer on opposite sides of the gate structure;
• patterning the ILD layer to form openings that expose a first 2D material layer over the semiconductor fin, wherein the gate spacer is in contact with a top surface of the first 2D material layer;
• and
• forming a second 2D material layer on the first 2D material layer through the openings until a combination of the second 2D material layer and the first 2D material layer comprises at least three or more monolayers of a 2D material.

A method, comprising:

• forming a semiconductor fin protruding above a substrate;
• forming a gate structure crossing the semiconductor fin;
• after forming the gate structure, forming a first 2D material layer on a top surface of the semiconductor fin exposed by the gate structure;
• forming gate spacers on opposite sidewalls of the gate structure and in contact with a top surface of the first 2D material layer;
• and
• after forming the gate spacers, depositing a second 2D material layer over the first 2D material layer until a combination of the second 2D material layer and the first 2D material layer comprises at least three or more monolayers of a 2D material.