Semiconductor devices and methods of formation

Abstract

A pixel sensor includes a transistor between a transfer transistor on a first semiconductor die and a source-follower gate on a second semiconductor die. The arrangement of the transistor may reduce input capacitance to the source-follower gate, which results in increased conversion gain in low-lighting conditions (e.g., high conversion gain mode) of a multiple semiconductor die image sensor device. A transistor between a first floating diffusion node coupled to the transfer transistor, and a second floating diffusion node coupled to the source-follower gate, may be turned off during signal readout from the source-follower gate, which blocks the signal path between the transistor and the transfer transistor. This prevents parasitic capacitance from the signal path from delaying and / or reducing the discharge of photocurrent from the second floating diffusion node onto the source-follower gate. As a result, substantially the full magnitude of the photocurrent can be applied to the source-follower gate.