A field-effect tunneling transistor based on vertical graphene heterostructures is reported, utilizing the low density of states in graphene and its single-atomic-layer thickness. The devices, composed of graphene heterostructures with boron nitride as a tunnel barrier, exhibit room temperature switching ratios of approximately 50, which can be enhanced by optimizing the device structure. These transistors show potential for high-frequency operation and large-scale integration. The performance of graphene-based field-effect transistors (FETs) has been limited by graphene's metallic conductivity at the neutrality point and Klein tunneling, which restricts ON-OFF switching ratios. To overcome this, the study proposes a field-effect transistor based on quantum tunneling through a thin insulating barrier, exploiting graphene's low density of states. The device structure includes a graphene electrode with a tunnel barrier of boron nitride, and the operation relies on the voltage tunability of the tunneling density of states and the effective height of the barrier. The devices were fabricated using a multistep process involving the transfer of monolayer graphene and hBN layers. The results show that the tunneling current is influenced by the tunneling density of states and the effective barrier height, with the tunneling current varying significantly with gate voltage. The study demonstrates that the tunneling devices offer a viable route for high-speed graphene-based analogue electronics, with ON-OFF ratios exceeding those of planar graphene FETs. The transit time for tunneling electrons through the nm-thick barriers is expected to be extremely fast, and the devices can be scaled down to the 10 nm scale for integrated circuits. The study also highlights the potential for further enhancement of ON-OFF ratios by optimizing the architecture and using higher-quality dielectrics.A field-effect tunneling transistor based on vertical graphene heterostructures is reported, utilizing the low density of states in graphene and its single-atomic-layer thickness. The devices, composed of graphene heterostructures with boron nitride as a tunnel barrier, exhibit room temperature switching ratios of approximately 50, which can be enhanced by optimizing the device structure. These transistors show potential for high-frequency operation and large-scale integration. The performance of graphene-based field-effect transistors (FETs) has been limited by graphene's metallic conductivity at the neutrality point and Klein tunneling, which restricts ON-OFF switching ratios. To overcome this, the study proposes a field-effect transistor based on quantum tunneling through a thin insulating barrier, exploiting graphene's low density of states. The device structure includes a graphene electrode with a tunnel barrier of boron nitride, and the operation relies on the voltage tunability of the tunneling density of states and the effective height of the barrier. The devices were fabricated using a multistep process involving the transfer of monolayer graphene and hBN layers. The results show that the tunneling current is influenced by the tunneling density of states and the effective barrier height, with the tunneling current varying significantly with gate voltage. The study demonstrates that the tunneling devices offer a viable route for high-speed graphene-based analogue electronics, with ON-OFF ratios exceeding those of planar graphene FETs. The transit time for tunneling electrons through the nm-thick barriers is expected to be extremely fast, and the devices can be scaled down to the 10 nm scale for integrated circuits. The study also highlights the potential for further enhancement of ON-OFF ratios by optimizing the architecture and using higher-quality dielectrics.