In this letter, for the first time, we proposed and demonstrated a novel tunnel dielectric-based tunnel FET (TD-TFET). Instead of using semiconductor band-to-band tunneling currents to form drive currents as in normal TFET, tunneling currents through ultrathin dielectric form the drive currents in the TD-TFET. The fabricated devices have achieved 55-mV/decade SS, which breaks the 60-mV/decade SS barrier. It has also realized higher than $1\,\,\times \,\,10^{\mathrm {\mathbf {5}}}~I_{\mathrm{{\scriptscriptstyle ON}}}/I_{\mathrm{{\scriptscriptstyle OFF}}}$ ratio. The unwanted ambipolar effect is greatly reduced, and OFF currents can be lowered to $1\,\,\times \,\, 10^{\mathrm {\mathbf {-14}}}$ A/ $\mu \text{m}$ level. These promising device characteristics make this novel TD-TFET very attractive for the future low standby power applications.