Characteristics of the electron temperature in the downstream regions of N-2/Ar ECR plasmas are discussed. The remarkable local heating of electrons was observed under certain experimental conditions of the magnetic field and the mixture ratio. The resulting electron temperature which was increased locally can influence the production of atomic nitrogen, which plays an important role for the nitridation process, especially at low pressure operation. As a result of the analysis of the experimental data, it is considered that the extraordinary wave (X-wave) contributed to the local heating due to the upper hybrid resonance (UHR). (c) 2005 Elsevier B.V. All rights reserved.