Transistors include a pyramid-shaped gate trench defined by a triangular shape or a trapezoidal shape in a channel width plane and a trapezoidal shape in a channel length plane. Side wall portions of the pyramid-shaped gate trench form a channel having a triangular shape or a trapezoidal shape in the channel width plane. Advantageously, such transistors increase transconductance without increasing pixel width. Devices, image sensors, and pixels incorporating such transistors are also provided, in addition to methods of manufacturing the same.