This study presents monolithically integrated high-density vertical organic electrochemical transistor (vOECT) arrays and complementary circuits. The research demonstrates a method for creating high-density (up to 7.2 million OECTs per cm²) and mechanically flexible vertical OECT arrays using electron-beam exposure to pattern organic semiconductors. The technique converts exposed semiconductor areas into electronic insulators while maintaining ionic conductivity and topological continuity with unexposed redox-active regions, essential for monolithic integration. The resulting p- and n-type vOECT active-matrix arrays exhibit transconductances of 0.08–1.7 S, transient times of less than 100 μs, and stable switching properties of more than 100,000 cycles. The study also fabricates vertically stacked complementary logic circuits, including NOT, NAND, and NOR gates. Organic electrochemical transistors (OECTs) and other organic semiconductor-based electronic components have potential applications in wearable electronics, biosensors, and neuromorphic devices due to their low driving voltages, excellent amplification and sensing capabilities, structural versatility, and potential for high-throughput production. However, conventional OECTs (cOECTs) have limited temporal and/or operational stability, slow redox processes, and poorly balanced p-(hole-transporting)/n-(electron-transporting) OECT performance, restricting their use in advanced signal processing for bioelectronics and multiplexed state-of-the-art electronics. Vertically stacked OECT architectures (vOECTs) have been developed to address these issues, but creating scalable patterning methods for the semiconductor materials and optimizing the architectural topology for efficient monolithic integration remains challenging. The study introduces a novel approach using direct electron-beam exposure of both p- and n-channel organic semiconductor (OSC) films to fabricate vOECT arrays. This method allows for high-resolution patterning without the need for masks, resists, or chemical solvents, eliminating potential damage to the OSC and reducing chemical waste. The approach enables the fabrication of ultra-small and high-density vOECTs with well-defined and patterned electronically active (conducting) channel regions due to the high-resolution of e-beam exposure. Additionally, multilayer integration of high-performance and high-density OECT structures is now possible due to the presence of planarized OSC films, which are topologically smooth and continuous. The study also demonstrates the fabrication of high-resolution vOECT active-matrix arrays with varying dimensions and the integration of vertically stacked complementary logic circuits. These circuits exhibit excellent performance and uniformity, with high transconductance and stable output logic levels. The vOECT arrays also show excellent stability under various bending radii and mechanical cycling deformations. The study concludes that the proposed vOECT platforms offer high performance and stability, making them suitable for use in biological systems, neuromorphic electronics, and wearable electronics.This study presents monolithically integrated high-density vertical organic electrochemical transistor (vOECT) arrays and complementary circuits. The research demonstrates a method for creating high-density (up to 7.2 million OECTs per cm²) and mechanically flexible vertical OECT arrays using electron-beam exposure to pattern organic semiconductors. The technique converts exposed semiconductor areas into electronic insulators while maintaining ionic conductivity and topological continuity with unexposed redox-active regions, essential for monolithic integration. The resulting p- and n-type vOECT active-matrix arrays exhibit transconductances of 0.08–1.7 S, transient times of less than 100 μs, and stable switching properties of more than 100,000 cycles. The study also fabricates vertically stacked complementary logic circuits, including NOT, NAND, and NOR gates. Organic electrochemical transistors (OECTs) and other organic semiconductor-based electronic components have potential applications in wearable electronics, biosensors, and neuromorphic devices due to their low driving voltages, excellent amplification and sensing capabilities, structural versatility, and potential for high-throughput production. However, conventional OECTs (cOECTs) have limited temporal and/or operational stability, slow redox processes, and poorly balanced p-(hole-transporting)/n-(electron-transporting) OECT performance, restricting their use in advanced signal processing for bioelectronics and multiplexed state-of-the-art electronics. Vertically stacked OECT architectures (vOECTs) have been developed to address these issues, but creating scalable patterning methods for the semiconductor materials and optimizing the architectural topology for efficient monolithic integration remains challenging. The study introduces a novel approach using direct electron-beam exposure of both p- and n-channel organic semiconductor (OSC) films to fabricate vOECT arrays. This method allows for high-resolution patterning without the need for masks, resists, or chemical solvents, eliminating potential damage to the OSC and reducing chemical waste. The approach enables the fabrication of ultra-small and high-density vOECTs with well-defined and patterned electronically active (conducting) channel regions due to the high-resolution of e-beam exposure. Additionally, multilayer integration of high-performance and high-density OECT structures is now possible due to the presence of planarized OSC films, which are topologically smooth and continuous. The study also demonstrates the fabrication of high-resolution vOECT active-matrix arrays with varying dimensions and the integration of vertically stacked complementary logic circuits. These circuits exhibit excellent performance and uniformity, with high transconductance and stable output logic levels. The vOECT arrays also show excellent stability under various bending radii and mechanical cycling deformations. The study concludes that the proposed vOECT platforms offer high performance and stability, making them suitable for use in biological systems, neuromorphic electronics, and wearable electronics.