The development of high-performance p-channel transistors remains a critical challenge in complementary logic circuits, despite significant advances in n-channel transistor technologies. While amorphous oxide semiconductors have revolutionized n-type transistors, achieving comparable performance for p-type counterparts has proven elusive. Here, this study demonstrates a breakthrough in p-channel technology by transforming crystalline 2D tellurium (2D-Te) into amorphous tellurium trioxide (a-TeO₃) through UV ozone treatment. This structural transformation, directly observed via high-resolution transmission electron microscopy, induces dramatic changes in electronic properties, including significant bandgap widening and enhanced work function. The resulting a-TeO₃-based p-channel transistors demonstrate remarkable improvements over crystalline 2D-Te transistors, featuring reduced hysteresis, superior on/off characteristics, and distinctive mobility behavior at different temperatures and gate fields. Most notably, these transistors achieve exceptionally low barrier height (10 meV) and sheet resistance values, while combining high hole mobility with excellent switching properties. The work not only introduces a novel high-performance p-channel semiconductor but also opens new avenues for phase engineering in advanced semiconductor development.