The present invention relates to a power semiconductor device structure and a fabrication process, and provides a high-performance RC-IGBT structure that can be fabricated without a thin wafer process. To achieve this objective, the present invention provides an RC-IGBT structure, including: an emitter electrode at the front surface; a plurality of cells under the emitter electrode; an n− drift region under the cells; a collector electrode located at the back surface; a plurality of trenches located at the back surface and being filled by the collector electrode; a mechanical support semiconductor region located between the trenches; a p+ collector region located at the top of each trench and connected to the collector electrode; an n buffer region located on top of each p+ collector region and below the n− drift region; and an n+ cathode region at the sidewall of each trench and connected to the collector electrode.