Structure and method for elimination of process-related defects in poly/metal plate capacitors

An integrated circuit includes silicon layer (2) supported by a bottom oxide layer (3), a shallow trench oxide (4) in the shallow trench (30), and a polycrystalline silicon layer (5) on the shallow trench oxide. A deep trench oxide (25) extending from the shallow trench oxide to the bottom oxide layer electrically isolates a section (2A) of the silicon layer to prevent a silicon cone defect (22) on the silicon layer from causing short-circuiting of the polycrystalline silicon layer to a non-isolated section of the silicon layer. The polycrystalline silicon layer can form a bottom plate of a poly /metal capacitor (20) and can also form a poly interconnect conductor.