Dual high-K oxides with SiGe channel

Abstract

A method and apparatus are described for integrating dual gate oxide (DGO) transistor devices (50, 52) and core transistor devices (51, 53) on a single substrate (15) having a silicon germanium channel layer (21) in the PMOS device areas (112, 113), where each DGO transistor device (50, 52) includes a metal gate (25), an upper gate oxide region (60, 84) formed from a second, relatively higher high-k metal oxide layer (24), and a lower gate oxide region (58, 84) formed from a first relatively lower high-k layer (22), and where each core transistor device (51, 53) includes a metal gate (25) and a core gate dielectric layer (72, 98) formed from only the second, relatively higher high-k metal oxide layer (24).

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention is directed in general to the field of semiconductor devices. In one aspect, the present invention relates to the fabrication of metal gate electrodes used in semiconductor devices.[0003]2. Description of the Related Art[0004]As semiconductor devices are scaled, aspects of device design and fabrication that previously gave rise to only second-order effects in long-channel devices can no longer be ignored. For example, the scaling of channel length and gate oxide thickness in a conventional MOS transistor exacerbates problems of polysilicon gate depletion, high gate resistance, high gate tunneling leakage current and dopant (i.e., boron) penetration into the channel region of the device. As a result, CMOS technology is increasingly replacing silicon dioxide gate dielectrics and polysilicon gate conductors with high dielectric constant (high-k) dielectrics in combination with metal gate electrodes fo...

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