Gate formation method for reduced poly-depletion and boron penetration

Abstract

Depletion of dopant from polysilicon gate layers with attendant dopant penetration of underlying gate oxide layers of silicon-based MOS and CMOS transistor devices are reduced or substantially eliminated by a process wherein a thin, high-quality silicon oxide gate insulator layer initially formed on a surface of a heavily-doped polysilicon substrate. The oxide layer is then subjected to impurity ion implantation selected to penetrate a desired depth into the underlying semiconductor substrate for formation of a structurally weakened cleavage plane thereat. The cleaved substrate is then bonded, via the silicon oxide gate insulator layer, to a second, lightly- to moderately-doped semiconductor substrate of similar conductivity type. The thus-produced composite is then subjected to further processing for patterning of the heavily-doped gate and gate insulator layers and to define active areas for formation of source/drain regions in the second, lightly-doped substrate.