Patent ID: 6916721

Claim:
A method for fabricating a trench capacitor with an insulation collar in a substrate, which is electrically connected to the substrate on one side via a buried contact, having a planar selection transistor which is provided in the substrate and is connected via the buried contact, comprising: providing a trench in the substrate using a hard mask with a corresponding mask opening; providing a capacitor dielectric in a lower and central trench region, the insulation collar in the central and upper trench region and an electrically conductive filling in the lower, central and upper trench region, a top side of the electrically conductive filling being sunk in the upper trench region with respect to the top side of the substrate; providing at least one liner on the hard mask and in the trench; carrying out an oblique implantation of impurity ions into the trench using the hard mask for altering the properties of a partial region of a topmost liner; forming a liner mask from the partial region or the complementary partial region of the topmost liner for defining a contact region on one side and an insulation region on a different side of the buried contact; and completing the connection region on the one side and the insulation region on the different side of the buried contact by removing and replacing a part of the filling and/or a part of the insulation collar using the liner mask.