MOSFET devices represented the basis of the electronics, but in the last years the scaling of the dimensions required by the technology caused the appearance of some problems, such as short channel effects and power dissipation. To overcome these drawbacks differ- ent solutions are possible and one of them is to change the nature of the device to TFET. Thanks to different conduction mechanism (tunneling) several advantages can be achieved; the most relevant are lower off-current, and so lower power dissipation, and smaller sub- threshold swing. In this thesis the design and the analysis of TFET devices are discussed through the use of the software Synopsys TCAD Sentaurus, by simulating realistic fabrication processes.