A semiconductor structure and a method for forming the semiconductor structure are provided. The method includes providing a substrate including a first region and a second region, and forming a plurality of fins over the first region. The method also includes forming an isolation layer over a front surface of the substrate, and forming a power rail opening by etching the isolation layer and a first portion of the second region. In addition, the method includes forming a through-hole by etching a second portion of the substrate, and forming a first metal layer in the power rail opening and the through-hole. Further, the method includes thinning a back surface of the substrate until the first metal layer is exposed, and back-etching the back surface of the substrate to enable a back surface of the first metal layer to be above the back surface of the substrate.