This paper deals with the performance analysis of Core-Shell (C-S) Junctionless (JL) FET structure in the RF domain application. The analysis begins with the non-quasi static (NQS) small signal model representation and from there the extraction of RF-parameters; and there after the harmonic distortions, linearity FOMs and Y-parameter are analyzed in detail. The device is investigated based on the variations of core/shell-thicknesses and shell-dopant concentrations. Y-parameters are evaluated from the NQS small signal model. In the RF domain analysis, the parameters such as, C gs , C gd , R gs , R gd , f T and τ m are assessed to determine its RF merits. Using the two-port equivalent model, the Y-parameters ( Y 11 , Y 12 , Y 21 , Y 22 ) are evaluated and investigated. The second and third order harmonic distortions ( HD 2 , HD 3 ) are calculated using IFM method and studied in detail. In addition to that, second, third harmonic intercept voltages ( VIP 2 , VIP 3 ) and third order intermodulation distortion ( IMD 3 ) are also assessed for its linearity performances in domain specific applications. The proposed device is designed using the Silvaco ATLAS TCAD . The device is calibrated with the experimental data that shows a close match between the two. The proposed device is found to exhibit good linearity and very low harmonic distortion behavior by modulating the shell-doping and thickness.