A method of forming a microelectronic device comprises forming a first microelectronic device structure comprising a first semiconductor structure, a first isolation material over the first semiconductor structure, and first conductive routing structures over the first semiconductor structure and surrounded by the first isolation material. 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 is bonded to the first isolation material 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. Control logic devices including transistors comprising portions of the first semiconductor structure are formed after forming the memory cells. Microelectronic devices, electronic systems, and additional methods are also described.