Abstract
Vertical three-dimensional (3D) integration is a highly attractive strategy to integrate a large number of transistor devices per unit area. This approach has emerged to accommodate the higher demand of data processing capability and to circumvent the scaling limitation. A huge number of research efforts have been attempted to demonstrate vertically stacked electronics in the last two decades. In this review, we revisit materials and devices for the vertically integrated electronics with an emphasis on the emerging semiconductor materials that can be processable by bottom-up fabrication methods, which are suitable for future flexible and wearable electronics. The vertically stacked integrated circuits are reviewed based on the semiconductor materials: organic semiconductors, carbon nanotubes, metal oxide semiconductors, and atomically thin two-dimensional materials including transition metal dichalcogenides. The features, device performance, and fabrication methods for 3D integration of the transistor based on each semiconductor are discussed. Moreover, we highlight recent advances that can be important milestones in the vertically integrated electronics including advanced integrated circuits, sensors, and display systems. There are remaining challenges to overcome; however, we believe that the vertical 3D integration based on emerging semiconductor materials and devices can be a promising strategy for future electronics.