<p>This study presents a breast cancer cell detector based on a dual cavity dielectric modulated (DM) silicon on insulator (SOI) junctionless field-effect transistor (DM-SOI-JL-FET), designed to detect various breast cancer cell types by incorporating a nanocavity structure. The nanocavity is created by etching the oxide region beneath the left and right sides of the gate. Also, the cavity thickness was optimized with respect to off-state current. Detection is achieved through analysing variations in the dielectric constant of the gate oxide when different breast cancer cells, such as MCF7-10&#xa0;A, HS578T, MDA-MD-231, MCF7, and T47D, are placed inside the cavity. Sensitivity (S) is calculated as the ratio of the off-state current (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\:{\text{I}}_{\text{O}\text{F}\text{F}}\)</EquationSource> </InlineEquation>) in the absence of breast cancer cells to the off-state current ​ in the presence of cancer cells. Additionally, variations in key electrical parameters, including drain current, energy band diagram, transconductance, and surface potential, are also evaluated with respect to different cancer cells. The results demonstrate that sensitivity increases with increase in the dielectric constant of the cancer cells. The sensitivity values for different cancer cells are as follows: MCF7-10&#xa0;A (14.09), MDA-MD-231 (91.37), HS578T (99.24), MCF7 (109.91), and T47D (118.58). This method enhances the breast cancer cell detection, demonstrating the potential of the DM-SOI-JL-FET detector for highly sensitive breast cancer diagnostics.</p>