Method for bonding two crystalline substrates together

A process for device fabrication is disclosed in which two substrates having different crystal lattices are bound together. In the process the substrate surfaces are thoroughly cleaned and placed in physical contact with each other. The duration of the contact and the pressure of the contact are selected to facilitate a bond between the two substrate surfaces that results from attractive Van der Waals' forces between the two surfaces. The bonded substrates are heated to a moderate temperature to effect escape of gases which may be entrapped by the substrates. The bulk of one of the substrates is then typically removed. The substrates can be heated again to a moderate temperature to effect removal of any gases remaining entrapped on the substrates. Thereafter, the bonded surfaces are heated to a high temperature to effect a permanent bond.