Abstract 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, Cgs, Cgd, Rgs, Rgd, fT and τm are assessed to determine its RF merits. Using the two-port equivalent model, the Y-parameters (Y11, Y12, Y21, Y22) are evaluated and investigated. The second and third order harmonic distortions (HD2, HD3) are calculated using IFM method and studied in detail. In addition to that, second, third harmonic intercept voltages (VIP2, VIP3) and third order intermodulation distortion (IMD3) 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.