This study presents the fabrication of high-density, vertically integrated organic electrochemical transistor (OECT) arrays and complementary circuits using electron-beam (e-beam) exposure to pattern organic semiconductors. The e-beam exposure technique allows for the creation of high-resolution, mechanically flexible OECT arrays with densities up to 7.2 million OECTs per cm². The method retains ionic conductivity while converting the exposed areas to insulators, enabling monolithic integration. The resulting p- and n-type OECT arrays exhibit transconductances of 0.08–1.7 S, transient times below 100 μs, and stable switching properties over 100,000 cycles. The study also demonstrates the fabrication of vertically stacked complementary logic circuits, including NOT, NAND, and NOR gates, achieving high performance and stability. The approach opens new possibilities for the integration of OECT circuits in biological systems, neuromorphic electronics, and wearable devices.This study presents the fabrication of high-density, vertically integrated organic electrochemical transistor (OECT) arrays and complementary circuits using electron-beam (e-beam) exposure to pattern organic semiconductors. The e-beam exposure technique allows for the creation of high-resolution, mechanically flexible OECT arrays with densities up to 7.2 million OECTs per cm². The method retains ionic conductivity while converting the exposed areas to insulators, enabling monolithic integration. The resulting p- and n-type OECT arrays exhibit transconductances of 0.08–1.7 S, transient times below 100 μs, and stable switching properties over 100,000 cycles. The study also demonstrates the fabrication of vertically stacked complementary logic circuits, including NOT, NAND, and NOR gates, achieving high performance and stability. The approach opens new possibilities for the integration of OECT circuits in biological systems, neuromorphic electronics, and wearable devices.