Complementary metal-oxide semiconductor (cmos) image sensors with saddle-gate source follower for imaging pixels

Abstract

A saddle-gate source follower transistor is described, such as for integration with in-pixel circuitry of complementary metal-oxide semiconductor (CMOS) image sensor (CIS) pixels. The saddle-gate source-follower transistor structure can include a channel region having a three-dimensional geometry defined on its axial sides by trenches. A gate oxide layer is formed over the top and axial sides of the channel region, and a saddle-gate structure is formed on the gate oxide layer. As such, the saddle-gate structure includes a seat portion extending over the top of the channel region, and first and second fender portions extending over the first and second axial sides of the channel region, such that the first and second fender portions are buried below an upper surface of the semiconductor substrate (e.g., buried into trenches formed in side isolation regions).