A junction-less transistor structure and fabrication method thereof are provided. The method includes providing a semiconductor substrate; and forming an epitaxial layer having a first surface and a second surface on the semiconductor substrate. The method also includes forming a plurality of trenches in the epitaxial layer from the first surface thereof; and forming a gate dielectric layer on side and bottom surfaces of the plurality of trenches. Further, the method includes forming a gate electrode layer on the gate dielectric layer and in the plurality of trenches; and forming an insulation layer on the gate electrode layer. Further, the method also includes forming a drain electrode layer on the first surface of the epitaxial layer; removing the semiconductor substrate; and forming a source electrode layer on the second surface of the epitaxial layer.