PURPOSE: To manufacture two pieces of the same wafer at a time to enable effective use of the wafer by adhering two semiconductor wafers with each other, having them subjected to desired surface treatment, and then separating them again.

CONSTITUTION: Two semiconductors 1, 1 are adhered to each other and subjected to desired surface treatment. Then the two adhered semiconductor wafers 1, 1 are separated from a joint face 3. in a process for adhering the two semiconductor wafers 1, 1, two wafers 1, 1 are adhered by means of-Si-0-Si- coupling and joint strength is formed to be approximately 50kg/cm2 or less. After the two wafers 1, 1 are subjected to various surface treatment, they are separated in release agent such as hydrofluoric acid solution. Thus two pieces of the wafer can be obtained at a time while a half of the wafer is not discarded by grinding and polishing so that effective use of the wafer is possible.