2D semiconductors, represented by transition metallic dichalcogenides (TMDs), have the potential to be various channel supplies for superior 3D field-effect transistors, resembling gate-all-around field-effect-transistors (GAAFETs) and complementary field-effect-transistors (C-FETs), because of their inherent atomic thinness, average mobility, and brief scaling lengths. Nonetheless, 2D semiconductors encounter a number of technological challenges, particularly the excessive contact resistance challenge between 2D semiconductors and metals. This assessment supplies a complete overview of the excessive contact resistance challenge in 2D semiconductors, together with its bodily background and the efforts to handle it, with respect to their applicability to GAAFET buildings.