Semiconductor stack having a dielectric sidewall for prevention of oxidation of tungsten in tungsten capped poly-silicon gate electrodes

摘要

In an integrated circuit, gate electrode stack of which is subjected to self-alignment processes, the sheet resistance is lowered by including a tungsten layer 15. The tungsten layer 14 is protected by a sidewall material 21 of SiNx or SiO2 after an etching step which did not extend to the substrate 11. During a subsequent etching step in which the stack extends to the substrate 11, the sidewall material 31 acts as a hard mask protecting the upper portion of the stack. After the lower portion of the stack is protected by a re-oxidation layer 41, the entire stack can be processed further without deterioration of the sheet resistance of the tungsten layer 15.