This invention provides a separation by implanted
oxygen (SIMOX) method for forming planar
hybrid orientation
semiconductor-on-insulator (SOI) substrates having different
crystal orientations, thereby making it possible for devices to be fabricated on
crystal orientations providing optimal performance. The method includes the steps of selecting a substrate having a base
semiconductor layer having a first crystallographic orientation separated by a thin insulating layer from a top
semiconductor layer having a second crystallographic orientation; replacing the top semiconductor layer in selected regions with an epitaxially grown semiconductor having the first crystallographic orientation; then using an
ion implantation and annealing method to (i) form a buried insulating region within the epitaxially grown semiconductor material, and (ii) thicken the insulating layer underlying the top semiconductor layer, thereby forming a
hybrid orientation substrate in which the two
semiconductor materials with different crystallographic orientations have substantially the same thickness and are both disposed on a common buried insulator layer. In a variation of this method, an
ion implantation and annealing method is instead used to extend an auxiliary buried insulator layer (initially underlying the base semiconductor layer) upwards (i) into the epitaxially grown semiconductor, and (ii) up to the insulating layer underlying the top semiconductor layer.