Various embodiments of the present application are directed towards a trench capacitor with a high capacitance density. In some embodiments, the trench capacitor overlies the substrate and fills a trench defined by the substrate. The trench capacitor comprises a lower capacitor electrode, a capacitor dielectric layer, and an upper capacitor electrode. The capacitor dielectric layer overlies the lower capacitor electrode and lines the trench. The upper capacitor electrode overlies the capacitor dielectric layer and lines the trench over the capacitor dielectric layer. The capacitor dielectric layer comprises a high κ dielectric material. By using a high κ material for the dielectric layer, the trench capacitor may have a high capacitance density suitable for use with high performance mobile devices.