**6.3. Fabrication issues**

The nanogap which is formed in a DM biosensor is carved out by forming a native oxide first, and then etching out the native oxide [38]. This method, however, is challenging, and practically, there is possibility that damages result from the process. These anomalies include creation of trap centers at the interface or incomplete etch of the native oxide along with traps in the residual gate dielectric [38]. The phenomenon of tunneling in a TFET is highly dependent on its source-channel tunnel junction, and the alignment of the gate with the junction. During fabrication, the gate edge may be displaced from the junction. This may result in an overlap or an underlap depending on whether the gate shifts towards the source or the channel respectively. In case of a gate-source overlap, the characteristics of the TFET generally improve as the shifted gate can now influence the energy bands in the source-channel junction with better control. However, in case of an underlap, the gate edge moves away from the junction, and the tunnel junction is least affected by it.
