Abstract: An apparatus is adapted to scribe a semiconductor wafer with a laser beam in only one direction of an axis. The apparatus includes an XY table for placing the wafer thereon, a laser beam oscillator provided above the XY table, and an optical system for permitting the laser beam to be directed onto the wafer on the XY table. In order to scribe the wafer in only one direction, the apparatus further includes a light interrupting switch adapted to permit the laser beam to pass when the XY table is moved in only one direction in synchronism with an XY table driving motor and to permit the laser beam to be interrupted when the XY table is moved in the other directions.

Abstract: The invention provides an SOS substrate for a semiconductor device wherein an epitaxial silicon layer which has an index of plane (100) is formed on a single crystal sapphire plate which has an index of plane (1012). An orientation flat is formed at an incline angle of 2.1 to 2.2.degree. with respect to a [011] or [011] direction on the surface of the epitaxial silicon layer which has the index of plane (100). The direction of the orientation flat on the surface of the sapphire plate is aligned with the direction of a cleavage plane of the sapphire plate.