Chemical Synthesis of Two-Dimensional Transition Metal Dichalcogenide Heterostructures and Superlattices and Their Applications in Transistor Devices

, have emerged as compelling candidates for next-generation integrated circuits (ICs) owing to their atomically thin geometry, dangling-bond-free surfaces, and tunable electronic properties. These intrinsic attributes enable them to overcome the fundamental limitations of traditional silicon-based semiconductors, such as short-channel effects in ultrascaled devices. Beyond single-component TMDs, the deliberate assembly of TMD building blocks into heterostructures and superlattices─with spatially defined chemical compositions, layer sequences, and electronic band alignments─unlocks unprecedented opportunities: not only for exploring fundamental quantum phenomena (e.g., interlayer excitons, moiré superconductivity) but also for developing high-performance electronic and optoelectronic devices with tailored functionalities. Specifically, lateral heterostructures (LHSs), formed by one-to-one covalent bonding between lattice-matched TMDs, enable high-density ultrathin ICs. In contrast, vertical heterostructures (VHSs) leverage van der Waals (vdW) intermolecular interactions to bypass strict lattice-matching constraints, allowing the integration of dissimilar TMDs (or other 2D materials like graphene and h-BN). The pristine, defect-free interfaces of vdW VHSs facilitate exceptional carrier transport, which are essential for low-power electronics. However, realizing the full potential of these systems hinges on the development of scalable synthesis strategies that can achieve atomically precise control over interface quality, composition distribution, and spatial patterning. This challenge is compounded by the extreme aspect ratios of 2D TMDs (ultrathin flakes with large lateral dimensions) and their high sensitivity to ambient conditions (e.g., oxidation, moisture adsorption) and synthetic environments (e.g., temperature, precursor concentration). This Account highlights recent advances in scalable synthesis of TMD heterostructures and superlattices, emphasizing strategies for achieving atomically sharp interfaces (lateral and vertical). We also emphasize advances in site-selective growth methodologies (e.g., clean defect/edge induced preferred nucleation and growth) that enable the fabrication of patterned architectures for preintegrated device arrays. Furthermore, we showcase the practical applications of these synthetic heterostructures with unique bandgap arrangement in high-performance, ultrachannel field-effect transistors (FETs), highlighting key performance enhancements compared to conventional single-component TMD devices. We further outline unresolved challenges in atomic-scale synthetic control toward future technologies.