As Moors law is concerned, down scaling of conventional CMOS technology results in, rapidly approaching fundamental limits. Alternative device structures are constantly proposed to substitute the traditional CMOS type devices. That type of device is a gated reverse-biased structure, commonly referred to as Tunnel Field-Effect Transistor (TFET). This device is particularly suitable for ultra-low-power applications. The most prominent feature of TFETs is their capacity for producing an inverse sub-threshold swing (SS) smaller than the 60 mV/decade thermal limit (at 300 K) of conventional inversion mode MOSFETs. Sub-thermal SS is achievable because, the drain current in TFETs is produced by carrier injection from source to channel which is predominantly governed by quantum mechanical band-to-band tunnelling (BTBT), rather than by diffusion as in MOSFETs. In, this paper we will show the silvaco TCAD simulation results for both conventional MOSFET and Tunnel field effect transistor. From the results, it is evident that TFET is suitable for ultra-low power applications.