Abstract: The Fermi level pinning effect at the interface between two-dimensional transition metal dichalcogenides（TMDs） and metals severely limits carrier transport efficiency.Phase transition engineering in 2D TMDs offers a breakthrough strategy for improving metal-semiconductor contacts. This work elucidates the physical mechanisms of phase transitions, revealing that lattice symmetry breaking（2H→1T/1T） synergistically optimizes three critical functionalities by reconfiguring interfacial electronic states and atomic arrangements:（1） suppression of metal-induced gap states（MIGS）,（2） modulation of band alignment, and（3） construction of atomically smooth interfaces. Systematic strategies for phase transition control are explored, including charge doping, external field stimuli, and thermodynamic regulation. Atomic intercalation stabilizes metallic phases by tailoring orbital electron filling, while external fields（optical, electrical, or strain） trigger lattice reconstruction through energy-momentum coupling. Alloying and thermodynamic synthesis enable spatially controlled growth of heterophases via energy barrier engineering. These approaches establish multiscale correlations among electronic states, lattice ordering, and interfacial transport, providing theoretical foundations for high-efficiency contacts in lowdimensional devices. Future challenges lie in achieving atomic-scale resolution of dynamic phase transitions, enhancing heterophase interfacial stability, and developing cross-scale integration processes. Addressing these issues will require multidisciplinary efforts to advance 2D electronic devices from fundamental innovation toward high-density integrated circuits.

Key words: phase engineering, contact resistance, field effect transistor, ohmic contact, schottky height