The present invention provides a method for fabricating a trench capacitor having an insulation collar (10; 10a, 10b) in a substrate (1), which is electrically connected to the substrate (1) on one side via a buried contact (15a, 15b), in particular for a semiconductor memory cell having a planar select transistor which is provided in the substrate (1) and is connected via the buried contact (15a, 15b), comprising the steps of: providing a trench (5) in the substrate (1) using a hard mask (2, 3) with a corresponding mask opening; providing a capacitor dielectric (30) in the lower and middle regions of the trench, the insulation collar (10) in the middle and upper regions of the trench and an electrically conductive filling (20) at least up to the top side of the insulation collar (10); completely filling the trench (5) with a filling material (50; 50′; 50″; 20); carrying out an STI trench production process; removing the filling material (50; 50′; 50″; 20) and lowering the electrically conductive filling (20) to below the top side of the insulation collar (10); forming an insulation region (IS; IS1, IS2) on one side with respect to the substrate (1) above the insulation collar (10); uncovering a connection region (KS; KS1, KS2) on the other side with respect to the substrate (1) above the insulation collar (10); and forming the buried contact (15a, 15b) by depositing and etching back a C filling (70; 70′; 70″; 70′″).