High-K dielectrics and metal gates are the key issues for MOS devices. In this study, electrical characteristics of MOS devices are improved by High-K gate dielectric and metal gate stacks. In the first part, experimental results show that electrical characteristics and reliability of MOS devices can be enhanced by proper High-K gate dielectric stacks. Al in HfAlO should be away from Si surface to reduce the effects of charge trapping. In the second part, the influences of MoN metal gate with TiN layer above or below and various post metal annealing (PMA) treatments were studied. Experimental results show that metal gate stack with TiN under MoN film (i.e., MoN⁄TiN sample) exhibits better electrical characteristics on gate leakage current, stress-induced flat-band voltage shift, and stress- induced leakage current and thermal stability despite a little lower work function. Thus MoN⁄TiN metal gate is promising for p-channel MOS device applications.