This paper proposes a highly sensitive nanoscale label-free biosensor upon charge plasma based gate-all-around nanowire dopingless field effect transistor (GAA NW DL FET Biosensor) for the detection of biomolecules. The proposed sensor device structure employs charge plasma and dopingless approaches to eliminate the requirement for doping. The thermionic emission of FET structures increases the device's current sensitivity (SI) for various targeted biomolecules introduced through the nanocavity created at the source side/metal of the proposed biosensor. To test the significant sensing performance of the device proposed herein, the biomolecules streptavidin with a dielectric constant (K) of 2.1, 3-aminopropyltriethoxysilane (APTES) with a K value of 3.57, and protein with a K value of 8 are utilized. The proposed sensor resulted in drain current sensitivity as high as 1.4 of protein biomolecule. An extensive analysis was performed to evaluate the efficiency of the proposed sensor with process-related issues such as cavity length variations ranging from 21nm to 3nm and real-time related issues such as fill factor variations ranging from 20% to 100 % and interface charges for the targeted biomolecules, and their sensitivity parameters were investigated, demonstrating the promising features of GAA NW DL FET biosensor as an ultrasensitive biosensor for clinical applications.