A 3D trenched-structure metal鈥搃nsulator鈥搈etal (MIM) nanocapacitor array with an ultrahigh equivalent planar capacitance (EPC) of 300 渭F cm鈥? is demonstrated. Zinc oxide (ZnO) and aluminum oxide (Al2O3) bilayer dielectric is deposited on 1 渭m high biomimetic silicon nanotip (SiNT) substrate using the atomic layer deposition method. The large EPC is achieved by utilizing the large surface area of the densely packed SiNT (5 脳 1010 cm鈥?) coated conformally with an ultrahigh dielectric constant of ZnO. The EPC value is 30 times higher than those previously reported in metal鈥搃nsulator鈥搈etal or metal鈥搃nsulator鈥搒emiconductor nanocapacitors using similar porosity dimensions of the support materials.