| abstract |
A semiconductor substrate having a silicon layer (24,26,28) is provided. In one embodiment, the substrate is a silicon-on-insulator (SOI) substrate (12,14,24,26,28) having an oxide layer (14) underlying the silicon layer (24,26,28). An amorphous or polycrystalline silicon germanium layer (32) is formed overlying the silicon layer (24,26,28). Alternatively, germanium is implanted into a top portion of the silicon layer (24,26,28) to form an amorphous silicon germanium layer (32). The silicon germanium layer (32) is then oxidized to convert the silicon germanium layer into a silicon dioxide layer (34) and to convert at least a portion of the silicon layer (24,26,28) into germanium-rich silicon (36,38). The silicon dioxide layer (34) is then removed prior to forming transistors (48,50,52) using the germanium-rich silicon (36,38). In one embodiment, the germanium-rich silicon (36,38) is selectively formed using a patterned masking layer (30) over the silicon layer (28) and under the silicon germanium layer (32). Alternatively, isolation regions may be used to define local regions of the substrate in which the germanium-rich silicon is formed. |