A dielectrically isolated semiconductor wafer substrate includes first and second semiconductive layers bonded to each other by a direct bonding technique in such a manner that an insulative layer is sandwiched therebetween. The first semiconductive layer is a first silicon layer having a (100) or (110) crystal surface orientation, while the second semiconductive layer is a second silicon layer having a (111) crystal surface orientation. Thereafter, a peripheral portion of the resultant substrate is removed, and a substrate of a slightly smaller size is obtained which is provided with an additionally formed new orientation flat.