BOTTLE-SHAPED TRENCH CAPACITOR WITH ENHANCED CAPACITANCE

In accordance with an aspect of the invention, a method is provided for fabricating a semiconductor chip including a trench capacitor. In such method, a monocrystalline semiconductor region can be etched in a vertical direction through an opening in a dielectric layer to form a trench exposing a rough surface of monocrystalline semiconductor material. The trench has an initial lateral dimension in a first direction transverse to the vertical direction. The semiconductor material exposed at the surface of the trench then is etched in a crystallographic orientation-dependent manner to expose a multiplicity of crystal facets of the semiconductor material at the trench surface. A dopant-containing liner may then be deposited to line the surface of the trench and a temperature of the substrate then be elevated to drive a dopant from the dopant-containing liner into the semiconductor region adjacent to the surface. During such step, typically a portion of the semiconductor material exposed at the wall is oxidized. At least some of the oxidized portion is removed to expose a wall of an enlarged trench, along which wall a dielectric layer and conductive material are formed in order to form a trench capacitor.