Si on Al2O3 bonded wafers refer to wafers where a layer of silicon has been bonded to a layer of aluminum oxide (Al2O3) using wafer bonding techniques. The aluminum oxide layer acts as an insulating layer, which can be used for various applications, such as for microelectromechanical systems (MEMS) devices or for creating high-k metal gate stacks for CMOS devices. The bond between the silicon and aluminum oxide layer is strong and reliable, making these bonded wafers suitable for a wide range of applications that require a robust and reliable interface between the silicon layer and an insulating layer.