Patent ID: 8435853

Claim:
A method for forming a trench gate field effect semiconductor device, comprising: providing a semiconductor body comprising a main horizontal surface and a gate electrode structure comprising a conductive region arranged in a deep trench disposed in the semiconductor body, the deep trench comprising, in a given vertical cross-section, a horizontal extension; forming an insulating layer on the main horizontal surface so that the insulating layer covers the conductive region; etching a narrow trench through the insulating layer so that a portion of the conductive region is exposed, the narrow trench comprising, in the vertical cross-section, a maximum horizontal extension smaller than the horizontal extension of the deep trench; and forming an integrated vertical poly-diode structure comprising a horizontally extending pn-junction, wherein forming the integrated vertical poly-diode structure comprises: depositing a polycrystalline semiconductor layer so that the narrow trench is completely filled; and maskless back-etching the polycrystalline semiconductor layer to form a polycrystalline region in the narrow trench.