RESULTS AND DISCUSSIONS Fig. shows a schematic of BioFET with the oxide region and the functionalized amino acid (Carboxylterminal Immobilized Aspartic Acid). SiO2, HfO2 and TiO2 have been selected as the gate oxides to analyze the effect of high-k dielectric on the sensitivity of the sensor. From Fig. (a), point-of- 6#$ 7 A Vs pH graphs for Arginine ,R/, Aspartic Acid ,D/ & Proline,P/ amino acids having SiO2 as gate oxide with Carboxyl group immobilized ,C-Imm/ and amine group immobilized ,N-Imm/ zero-charge (pHpzc) for SiO2, HfO2 and TiO2 are clearly understood as the pH at which the zeta potential crosses the zero value. As shown in Fig. (b), α is minimum at pHpzc but for HfO2 it's around 0.6 (higher than SiO2 and TiO2) since the change in Ψξ w.r.t. pH is higher for enhanced sensitivity. Also, the increment in α is observed for all gate oxides before and after pHpzc. β has a similar trend w.r.t. pH as it denotes the change in : w.r.t. pHS [Fig. ]. Fig. (a) shows the Ψ0 variation for all three gate oxides considered which follows the Ψξ with the drop across the stern layer. Fig. ) is the 2 nd order gradient of Ψo that shows the transition of reactive sites over the oxide from protonation to deprotonation clarifying the pHpzc value. Fig. shows the total capacitance ,; < ) which consists of stern capacitance, diffuse-layer capacitance and intrinsic oxide capacitance. TiO2 shows better resolution for ion-sensing with higher capacitance and non-linearity of Ψo due to the large difference between the affinity constants. Considering the full coverage, Fig. represents the depletion width, drain current (ISD) and 2 nd order gradient of ISD = 6 7 > ?@ 6#$ 7 A for SiO2 which varies depending on the affinities of Carboxyl/Amine-term. immobilized Aspartic Acid ,D/ [ ], Arginine ,R/ [ ], and Proline ,P/ [ ]. Different site-binding relations are used to calculate the Ψo. The affinity of the remaining amine/carboxyl sites and sidechains are responsible for the distinct fingerprints for the amino acids in the form of ISD and 6 7 > ?@ 6#$ 7 . Such a simplified model can enhance the possibility of using FET-based sensors for model proteomics.