The present disclosure provides devices and methods in which a semiconductor chip has a reduced size and thickness. The device is manufactured by utilizing a sacrificial or dummy silicon wafer. A recess is formed in the dummy silicon wafer where the semiconductor chip is mounted in the recess. The space between the dummy silicon wafer and the chip is filled with underfill material. The dummy silicon wafer and the backside of the chip are etched using any suitable etching process until the dummy silicon wafer is removed, and the thickness of the chip is reduced. With this process, the overall thickness of the semiconductor chip can be thinned down to less than 50 μm in some embodiments. The ultra-thin semiconductor chip can be incorporated in manufacturing flexible/rollable display panels, foldable mobile devices, wearable displays, or any other electrical or electronic devices.