An image sensor includes an image sensor pixel array having pixels. Each pixel includes a continuous active region having a first portion and a second portion extending from the first portion. A photodiode, a reset transistor, a drive transistor, and a select transistor are formed in and over the first portion. The photodiode and the reset transistor define a floating diffusion region therebetween. A switch transistor is formed in and over the second portion and includes a first source/drain region and a second source/drain region. The first source/drain region is included in the floating diffusion region. The second source/drain region interfaces a doped region formed in the second region. The pixel also includes a gate structure disposed directly over the doped region. By controlling the switch transistor, the pixel may operate in a high conversion gain mode or a low conversion gain mode to accommodate different illumination or exposure conditions.