A trench-gate source-follower (TGSF) transistor is described, such as for integration with image sensor pixels. The TGSF transistor is at least partially built into a trench etched into a substrate. A contiguous doped region is implanted around the inner walls of the trench to form a buried-trench current channel. A trench-gate is formed to have at least a buried portion that fills the volume of the trench. A gate oxide layer can be disposed between the buried portion of the trench-gate and the buried-trench current channel. Drain and source regions are formed on either end of the trench-gate. Activating the trench-gate causes current to flow between the drain and source regions via the buried-trench current channel around the buried portion of the trench-gate. The geometry of the buried-trench current channel can effectively increase the width of the active region of the source-follower transistor without increasing its physical layout width.