This work introduces a novel SG-HKQSTFET (Shifted-Gate High-k Quad-Segment Tunnel Field-Effect Transistor) biosensor designed for ultra-sensitive and label-free biomolecule detection. The structure incorporates a P⁺ source, N⁺ drain, and a segmented P-type channel that includes four vertical regions: \({\text{V}}_{1}\) , \({\text{V}}_{3}\) , and \({\text{V}}_{4}\) as intrinsic and undoped, while \({\text{V}}_{2}\) is n-type doped to support efficient band-to-band tunneling. A dual-gate configuration with a nanogap sensing cavity provides improved electrostatic control, while the \({\text{HfO}}_{2}\) / \({\text{SiO}}_{2}\) dielectric stack strengthens gate coupling and the electric field at the source–channel junction. The shifted-gate architecture further modifies the electric field distribution to improve tunneling efficiency and current conduction. TCAD simulations using Silvaco Atlas under biased and unbiased conditions show that the biased shifted-gate configuration achieves the best performance, with an \({\text{I}}_{\text{ON}}/{\text{I}}_{\text{OFF}}\) ratio of 1.16 × 1012, a low subthreshold swing (SS) of 16.7 mV/dec, and a transconductance ( \({\text{g}}_{\text{m}}\) ) of 1.35 × 10⁻5 A/V for the MDA-MB-231 biomolecule (K = 22), demonstrating the biosensor’s potential for reliable biomolecule detection.
