A nitride-isolated molybdenum-polysilicon gate electrode for MOS VLSI circuits

A new gate electrode structure is demonstrated. The low-resistive gate electrode consists of a triple layer of molybdenum and polysilicon films isolated with an ultrathin silicon-nitride film, namely MTP-metal/tunneling nitride/polysilicon. The tunneling nitride, which is grown by direct thermal nitridation of silicon, avoids silicidation of molybdenum and diffusion of impurities resulting in a thin SiO2film of good quality. Characteristics of discrete FET's can be designed like those of conventional silicon-gate devices. No instability due to the tun, neling nitride has been observed in both dc and high-speed switching operations. The technique is useful for MOS VLSI circuits.