A method includes: forming a dielectric fin protruding above a substrate; forming a channel layer over an upper surface of the dielectric fin and along first sidewalls of the dielectric fin, the channel layer including a low dimensional material; forming a gate structure over the channel layer; forming metal source/drain regions on opposing sides of the gate structure; forming a channel enhancement layer over the channel layer; and forming a passivation layer over the gate structure, the metal source/drain regions, and the channel enhancement layer.