Abstract: A semiconductor device includes a trench disposed in an epitaxial layer on a substrate. A gate structure is disposed in the trench and includes upper and lower conductive portions. A dielectric isolation portion is disposed between the upper and lower conductive portions. A dielectric liner is disposed in the trench and has an opening on the bottom surface of the trench. The opening is filled up with a part of the lower conductive portion. A portion of the epitaxial layer and the lower conductive portion construct a Schottky barrier diode. A doped region is disposed in the epitaxial layer, under the bottom surface of the trench and on one side of the lower conductive portion. The portion of the epitaxial layer and a portion of the doped region are in contact with the lower conductive portion.