Embodiments of semiconductor devices and fabrication methods thereof are disclosed. In an example, a method for forming a semiconductor device is disclosed. First semiconductor structures are formed on a first wafer. At least one of the first semiconductor structures includes a processor and a first bonding layer including first bonding contacts. Second semiconductor structures are formed on a second wafer. At least one of the second semiconductor structures includes an array of SRAM cells and a second bonding layer including second bonding contacts. The first wafer and the second wafer are bonded in a face-to-face manner, such that the at least one of the first semiconductor structures is bonded to the at least one of the second semiconductor structures. The first bonding contacts of the first semiconductor structure are in contact with the second bonding contacts of the second semiconductor structure at a bonding interface. The bonded first and second wafers are diced into dies. At least one of the dies includes the bonded first and second semiconductor structures.