Ta<inf>2</inf>O<inf>5</inf>/SiO<inf>2</inf> stacked gate dielectric for silicon MOS devices

Dielectric materials with permittivity higher than that of SiO2 are becoming increasingly important in ULSI technology as they allow the physical thickness of the gate dielectric to be higher while maintaining the same gate capacitance as in a conventional MOS process. This reduces the gate leakage current, which has become a serious problem in modern MOSFETs with a gate oxide thickness less than 4 nm. In this paper we present the characteristics of MTOS capacitors with a Ta2O5/SiO2 stacked dielectric layer and compare the results with MOS capacitors having an equivalent dielectric thickness. It is shown that the leakage current is considerably smaller and the breakdown voltage significantly higher in the MTOS devices.