Semiconductor device and fabrication method thereof

A method for fabricating a semiconductor device, comprising:

• providing a substrate having thereon an etch stop layer, a first dielectric layer on the etch stop layer, and a hard mask layer on the first dielectric layer;
• forming a trench in the hard mask layer and the first dielectric layer;
• forming a first source/drain electrode layer on a sidewall of the trench, wherein the first source/drain electrode layer extends along the sidewall and a bottom of the trench;
• forming a second dielectric layer to cover the first source/drain electrode layer in the trench;
• forming a second source/drain electrode layer on the second dielectric layer in the trench;
• forming a third dielectric layer on the second source/drain electrode layer in the trench;
• forming a two-dimensional (2D) material layer overlying the hard mask layer, the first source/drain electrode layer, the second dielectric layer, the second source/drain electrode layer, and the third dielectric layer;
• forming a gate dielectric layer on the 2D material layer;
• and
• forming a gate electrode on the gate dielectric layer.