What is a MOS field effect tube?

MOS field effect tube is a metal-oxide-semiconductor field effect tube, abbreviated as MOSFET (Metal-Oxide-Semiconductor Field-Effect-Transistor), which belongs to the insulated gate type.

　　

　　 Its main feature is that there is a silicon dioxide insulating layer between the metal gate and the channel, so it has a very high input resistance (up to 1015Ω). It is also divided into N-channel tube and P-channel tube. Usually the substrate (substrate) and the source S are connected together.

　　

　　 According to the different conduction mode, MOSFET is divided into enhancement type and depletion type.

　　

The so-called enhanced type refers to: when VGS=0, the tube is in an off state, and after adding the correct VGS, the majority of carriers are attracted to the gate, thereby "enhancing" the carriers in this area and forming a conductive channel .

　　

　　 depletion type means that when VGS=0, a channel is formed, and when the correct VGS is added, most carriers can flow out of the channel, thus "depleting" the carriers and turning the tube off.

　　

　　Winsok MOS field effect transistor

　　

　　Take the N channel as an example, it is made two high doping concentration source diffusion area N+ and drain diffusion area N+ on the P-type silicon substrate, and then lead out the source S and drain D respectively. The source and the substrate are connected internally, and the two always maintain the same potential. When the drain is connected to the positive pole of the power supply and the source is connected to the negative pole of the power supply and VGS=0, the channel current (ie drain current) ID=0. As VGS gradually increases, attracted by the positive voltage of the gate, negatively charged minority carriers are induced between the two diffusion regions, forming an N-type channel from the drain to the source. When VGS is greater than the tube When the turn-on voltage VTN (generally about +2V) is reached, the N-channel tube begins to conduct, forming a drain current ID.

　　

　　VMOS field effect tube (VMOSFET) is referred to as VMOS tube or power field effect tube, its full name is V-groove MOS field effect tube. It is a high-efficiency, power switching device newly developed after MOSFET. It not only inherits the high input impedance of the MOS field effect tube (≥108W), small drive current (about 0.1μA), but also has high withstand voltage (up to 1200V), high working current (1.5A～100A), and output High power (1～250W), good linearity of transconductance, and fast switching speed. It is precisely because it combines the advantages of electron tubes and power transistors into one, it is being widely used in voltage amplifiers (voltage amplification up to thousands of times), power amplifiers, switching power supplies and inverters.

　　

　　As we all know, the gate, source, and drain of a traditional MOS field effect transistor are on a chip whose gate, source, and drain are roughly on the same horizontal plane, and its working current basically flows in the horizontal direction. VMOS tubes are different, with two major structural features: first, the metal gate adopts a V-groove structure; second, it has vertical conductivity. Since the drain is drawn from the back of the chip, the ID does not flow horizontally along the chip, but starts from the heavily doped N+ region (source S), flows through the P channel into the lightly doped N- drift region, and finally reaches vertically downwards Drain D. Because of the increased cross-sectional area, large currents can be passed. Because there is a silicon dioxide insulating layer between the gate and the chip, it is still an insulated gate MOS field effect transistor.