Highly reliable single crystal semiconductor layers and semiconductor devices can be obtained through a fewer manufacturing steps. A method for manufacturing a semiconductor device is proposed. A single crystal semiconductor substrate provided with an insulating film is irradiated with an ion beam to form a damaged region in the single crystal semiconductor substrate; liquid glass is floated over a liquid denser than the liquid glass to shape the liquid glass into a plate; the single crystal semiconductor substrate provided with the damaged region is placed over the plate-like liquid glass so that the insulating film and the liquid glass face each other; the plate-like liquid glass and the single crystal semiconductor substrate are cooled slowly, whereby a glass substrate is obtained from the plate-like liquid glass and concurrently the glass substrate and the single crystal semiconductor substrate are bonded together; and a single crystal semiconductor layer is separated from the single crystal semiconductor substrate along the damaged region.