A microelectronic device comprises a die comprising a front side and a back side opposite the front side, one or more components of integrated circuitry within a base material of the die and between the front side and the back side of the die, and one or more decoupling capacitors within the back side of the die. The one or more decoupling capacitors comprise a first electrode, a second electrode, and a dielectric material between the first electrode and the second electrode. The microelectronic device further comprises a first conductive via comprising a conductive material extending through the base material, the first conductive via in electrical communication with the first electrode of the one or more decoupling capacitors and the front side of the microelectronic device. Related apparatuses including a decoupling capacitor in a back side, and related electronic systems and methods are also described.