The present disclosure provides semiconductor structures and fabrication methods thereof. An exemplary fabrication method includes providing a substrate having a first region and a second region; forming a trench in the substrate in the first region; forming a compensation doping region in a side surface of the trench adjacent to the second region; forming an isolation structure in the trench; forming a well region in the substrate in the second region; forming a drift region in the substrate in the first region; forming a gate structure over the substrate in a boundary region between the first region and the second region, and covering a portion of the isolation structure; and forming a source region in the well region at one side of the gate structure and a drain region in the drift region at another side of the gate structure.