A field effect semiconductor device comprising a high permittivity hafnium (or hafnium-zirconium) nitride gate dielectric and a method of forming the same are disclosed herein. The device comprises a silicon substrate 20 having a semiconducting channel region 24 formed therein. A hafnium (or hafnium-zirconium) nitride gate dielectric layer 36 is formed over this substrate, followed by a conductive gate 38. Hafnium (or hafnium-zirconium) nitride gate dielectric layer 36 has a dielectric constant is significantly higher than the dielectric constant of silicon dioxide.