A method of forming a microelectronic device comprises forming a first microelectronic device structure comprising a first semiconductor structure, control logic circuitry including transistors at least partially overlying the first semiconductor structure, and a first isolation material covering the first semiconductor structure and the control logic circuitry. A second microelectronic device structure comprising a second semiconductor structure and a second isolation material over the second semiconductor structure is formed. The second isolation material of the second microelectronic device structure is bonded to the first isolation material of the first microelectronic device structure to attach the second microelectronic device structure to the first microelectronic device structure. Memory cells comprising portions of the second semiconductor structure are formed after attaching the second microelectronic device structure to the first microelectronic device structure. Microelectronic devices, electronic systems, and additional methods are also described.