The ability to control the electron flow of a Metal-Oxide-Semiconductor Field-Effect Transistor MOSFET decreases due to a quantum mechanical effect as the size decreases below 50 nm. To meet this challenge, a new area of device research is needed. One such area is devices based on tunneling phenomena, called single-electron devices. In this paper, the most fundamental single-electron device, the Single Electron Transistor (SET), is designed using visual Technical Computer Aided Design (TCAD) with a gate length of 2 nm and a gate width of 2 nm. The channel is ultra-thin with a length of 2 nm and a width of 0.005 nm, and the thickness of the channel is 0.3 nm. Then, a Si quantum dot with a size of 0.5 * 1.6 nm2 is used between the island and the gate. Both devices are successfully simulated using Genius Simulator. It has been established that a device with a silicon dot is more promising at room temperature. A device with a silicon dot has a lower capacity and higher charging energy than a device without a quantum dot.