A method of manufacturing a semiconductor device having an active region and a termination region includes providing a semiconductor substrate having first and second main surfaces opposite to each other. The semiconductor substrate has an active region and a termination region surrounding the active region. The first main surface is oxidized. A first plurality of trenches and a first plurality of mesas are formed in the termination region. The first plurality of trenches in the termination region are filled with a dielectric material. A second plurality of trenches in the termination region. The second plurality of trenches are with the dielectric material.