Recent etching processes often use low to middle plasma density in order to increase etching controllability or to reduce charging damages. In inductively coupled plasmas (ICPs) in low to middle plasma density, effects of a capacitively coupled discharge (E discharge) on the total plasma characteristic cannot be neglected. It is thus more difficult to understand the ICPs in low to middle density than to understand high-density ICPs which can be regarded as being generated by an inductively coupled discharge (H discharge) only. In this research, we changed the voltage distribution of the induction coil of an ICP-modified gaseous electronics conference reference cell by inserting a termination capacitor between the coil and the ground. We also changed the discharge frequencies (6.28 MHz, 13.56 MHz, and 20 MHz), and investigated their effects on Ar plasmas. As a result, it was observed that the structure of the E discharge was changed by the voltage distribution of the coil and, therefore, E-to-H mode transitions were dramatically altered. Although no difference between the electron energy distribution functions (EEDFs) was observed in a pure H discharge with an electrostatic shield for the experimental conditions studied (1.33 Pa and 150 W), it was observed that EEDFs were affected by the discharge frequency without an electrostatic shield, probably due to a decrease of electron density by the effect of an E discharge and an increase of the ratio of the E to H discharge with increasing discharge frequency. (C) 2004 American Vacuum Society.