MOSFET device fabrication method capable of allowing application of self-aligned contact process while maintaining metal gate to have uniform thickness

摘要

The MOSFET fabrication method allows application of a self-aligned contact (SAC) process while maintaining a metal gate, such as a tungsten gate, to have a uniform thickness. The process involves forming a metal oxide film during the formation of a metal gate structure of the MOSFET device. The metal oxide film is formed by subjecting the gate structure through a rapid thermal oxidation (RTO) treatment and then to an N₂O plasma treatment. The treatments allow the thickness of the metal oxide to be precisely controlled. The metal oxide acts as an insulator, which prevents electrical shorts between the gate structure and a contact plug even if a misalignment of occurs during the SAC process. This is an improvement from the conventional practice of separately forming a SAC barrier film after the formation of the metal gate structure and thus saves money, time, and increases reliability and productivity. Also the performance characteristics of the device is enhanced.