A method for forming a bottle trench. First, a substrate covered by a photoresist layer is rotated to a specific angle prior to performance of lithography, thereby forming a rectangular opening in the photoresist layer and exposing the substrate, in which edges of the rectangular opening are substantially parallel to the {110} plane of the substrate due to the rotation of the substrate. Next, the exposed substrate is etched to form a trench therein, in which the sidewall surface of the trench is the {110} plane of the substrate. Finally, isotropic etching is performed on the substrate of the lower portion of the trench using an etching shield layer formed on the sidewall of the upper portion of the trench as an etching mask, to form the bottle trench. The invention also discloses a method of fabricating a bottle trench capacitor.