Abstract: Due to market demand， the integration level of integrated circuits on Si substrates becomes higher and higher.However, improvements in the degree of integration is based on reduction of the dimensions of the fundamental active device in the circuit——the metal－oxide－semiconductor field effect transistor (MOSFET). When the SiO2 layer of the gate is thinner than the size of an atom， it may not have the required insulating properties as a result of quantum effects. Hence we must search for a new high dielectric (high－K) oxide material to replace the conventional SiO2. Today, efforts to find such new oxides are ongoing in many countries of the world. In this paper we describe how the properties of MOSFETs are affected when the SiO2 layer thickness decreases， indicate the requirements and choice of alternative high－K oxide materials， and give an overview of recent research activities.