Negative differential conductance based on lateral band‐to‐band tunneling is demonstrated in a three‐terminal silicontunneling device. The device is fabricated with the current silicon ultra‐large scale integration (Si ULSI) process, taking care of the field isolation to reduce the excess tunneling current that flows over some intermediate states. It is observed that the forward biased band‐to‐band tunneling current is largely controlled by the gate bias which modulates the tunneling barrier width. The three‐terminal Si tunneling device is promising as the post complementary metal–oxide‐semiconductor device in future Si ULSI.