a buried transistor particularly suitable for soi technology , where the transistor is fabricated within a trench in a substrate and the resulting transistor incorporates completely isolated active areas . the resulting substrate has a decreased topography and there is no need for polysilicon plugs to connect to the transistor , unless desired . with this invention , better control is achieved in processing , particularly of gate length . the substrate having the buried transistor can be silicon oxide bonded to another substrate to form an soi structure .