Power devices (PD) are ubiquitous elements of the modern electronics industry that must satisfy the rigorous and diverse demands for robust power conversion systems that are essential for emerging technologies including Internet of Things (IoT), mobile electronics, and wearable devices. However, conventional PDs based on “bulk” and “single-crystal” semiconductors require high temperature (>1000°C) fabrication processing and a thick (typically a few tens to 100 μm) drift layer1, thereby preventing their applications to compact devices2, where PDs must be fabricated on a heat sensitive and flexible substrate. Here we report next-generation PDs based on “thin-films” of “amorphous” oxide semiconductors with the performance exceeding the silicon limit (a theoretical limit for a PD based on bulk single-crystal silicon3). The breakthrough was achieved by the creation of an ideal Schottky interface without Fermi-level pinning at the interface, resulting in low specific on-resistance Ron,sp (<1×10-4 Ωcm2) and high breakdown voltage VBD (~100 V). To demonstrate the unprecedented capability of the amorphous thin-film oxide power devices (ATOPs), we successfully fabricated a prototype on a flexible polyimide film, which is not compatible with the fabrication process of bulk single-crystal devices. The ATOP will play a central role in the development of next generation advanced technologies where devices require large area fabrication on flexible substrates and three-dimensional integration.