L-Shaped Fin Field Effect Diode for ESD and Alignment

The patent transitions from a planar diode structure to a three-dimensional vertical fin structure. The p-n junction is formed vertically through the fin body, with the anode and cathode positioned at different heights along the fin, eliminating the need for precise lateral alignment of multiple impurity regions and gates in the same plane. This vertical stacking approach resolves the alignment precision issue by operating in a different spatial dimension.

The fin structure is segmented into distinct functional regions: the anode region at the top, the p-n junction region in the middle, and the cathode region at the bottom. This segmentation allows each region to be formed and doped independently through sequential processing steps, simplifying the manufacturing process and reducing alignment complexity compared to forming multiple closely spaced impurity regions simultaneously.

The gate structure in the vertical fin diode serves multiple functions simultaneously: it controls the current flow through the p-n junction, provides electrostatic discharge protection, and enables the diode to operate in different modes (rectification, breakdown, etc.). This multi-functionality reduces the need for separate dedicated ESD protection structures, thereby managing device complexity while enhancing ESD performance.

The patent combines the ESD protection function with the primary current control function in a single gate structure. Rather than adding separate ESD protection devices, the gate is designed to perform both rectification control and ESD clamping, merging multiple protective functions into one element and reducing overall device complexity.