Metal-semiconductor plasmonic metasurfaces enable precise optical field manipulation at the subwavelength scale; however, most existing designs rely on external fields and exhibit only binary responses, thereby restricting the realization of multistate logic operations. Here, we present an in-situ polarization-controlled approach based on an Au–indium tin oxide (ITO) bilayer nanocrescent with a Schottky heterojunction for achieving polarization-dependent tristate optical modulation. Polarization-selective excitation of distinct localized plasmon modes facilitates directional hot-electron injection across the Au–ITO interface, thereby producing three distinct programmable states—positive, zero, and negative—at a single detection wavelength. This symmetric bilayer design is applicable to other metal-semiconductor composites and offers generalizable design principles for ternary logic, multistate optical encoding, and ultrafast photonic information processing. The proposed concept is validated through both experimental measurements and numerical simulations.