A deep trench capacitor structure including an SOI substrate comprising an SOI layer, a rare earth oxide layer, and a bulk substrate, the rare earth oxide layer is located below the SOI layer and above the bulk substrate, and the rare earth oxide layer insulates the SOI layer from the bulk substrate, and a deep trench capacitor extending from a top surface of the SOI layer, through the rare earth oxide layer, down to a location within the bulk substrate, the rare earth oxide layer contacts the deep trench capacitor at an interface between the rare earth oxide layer and the bulk substrate forming an incline away from the deep trench capacitor.