To tackle the industry bottleneck of excessively high contact resistance between two-dimensional semiconductors and metal electrodes—where selenium vacancies within tungsten diselenide impede hole transport—a joint team from Huazhong University of Science and Technology and the National University of Singapore pioneered a novel controllable oxygen doping approach. In this process, metal electrodes are first fabricated and subsequently annealed in oxygen, enabling oxygen to diffuse in and fill selenium vacancies, optimize the interfacial electronic structure, reduce the contact resistance of tungsten diselenide by approximately 94%, and dramatically enhance hole mobility. A 16-nanometer-channel tungsten diselenide p-type transistor fabricated using this process achieved a ballistic transport ratio of 81% at room temperature, surpassing state-of-the-art silicon-based devices of comparable dimensions and removing a key obstacle to the development of sub-1-nanometer chips. At present, however, this achievement still requires resolving engineering challenges—such as compatibility with high-k insulating layers and large-scale uniform growth of two-dimensional materials—before industrialization can be realized.