?1、In the last few year, the metal-oxide-semiconductor(MOS) transistor has emerged ai the most important electronic device, superseding the bipolar junction transistor in sales volume and applications.
Its strength devices form its simple structure and low fabrication cost. for these reasons, the MOS transistor should continue to be the most popular device for very large scale integration and mass-production products.
In this chapter,we discuss the basic operation of the most important class of FETs: the si-based insulated-gate field-effect transistor(IGFET).The gate material in these devices was originally a metal(aluminum) ant the insulator was silicon dioxide(Sio2). That is the origin of the term metal-oxide-semiconductors field-effect transistor, or MOSFET.
For ease of fabrication and reproducibility, however, the current practice is to use degenerately doped polycrystalline Si(poly Si),which is highly conductive, instead of metal for the gate.
In n-channel devices, n+poly-Si is used for the gates, and p+poly -Si is used for p+channel devices. Silicon dioxide is still usually used for the insulator ,although nitrogen is sometimes incorporated into the SiO2 to increase its dielectric constant(and thus device performance).
While the term IGFET is a more accurate description, in this book we adopt the practice common in the industry, which is to use the more common term MOSFET
to describe this class of devices.
1在过去的几年年中，金属氧化物半导体（MOS ）晶体管已经成为人工智能中最重要的电子设备，取代了双极结型晶体管的销量和应用。
其实力器件构成其结构简单，造价低。由于这些原因，MOS晶体管应当继续成为超大规模集成电路和大规模生产的产品，最流行的设备。
在本章中，我们将讨论FET的最重要的一类的基本操作：在Si基绝缘栅场效应晶体管（绝缘栅场效应晶体管），在这些设备的栅极材料原本是一个金属（铝）蚂蚁绝缘体是硅二氧化硅（SiO 2 ） 。也就是说，术语金属 - 氧化物 - 半导体场效应晶体管，或MOSFET的原点。
为便于制作和再现性，但是，目前的做法是使用简并掺杂的多晶硅（多晶Si ），这是高导电性的，而不是用于金属栅极。
在n沟道型器件中，n +多晶Si是用于门，和p +多晶Si是用于P +沟道器件。二氧化硅仍是通常用于绝缘体，虽然氮有时掺入二氧化硅，以增加它的电介质常数（因此器件的性能） 。
而术语绝缘栅场效应晶体管是一个更准确的描述，在这本书中，我们采用通用的做法在行业内，这是使用更常见的术语的MOSFET
来形容这个类的设备。
2 We considered the threshold voltage Vt to be the gate voltage that would be required to just form a good conducting channel. While
this parameter can be determined experimentally once the device is made, it is dependent on the various material properties of the device and it its value can be controlled during fabrication.
As discussed in "Definition of Threshold ", the threshold voltage is defined as the gate voltage required producing a surface potential of &s=2&f at the source end of the channel.
It is the gate voltgate that produces a carrier concentration at the surface at the source end of the channel equal to, but opposite in sign to, that in the substrate.
This surface potential is dependent on the work function difference between the gate and the substrate, and the oxide thickness. in addition to these previously discussed causes of the surface potential,there can be charges in the material below the gate..
2 ，我们认为是阈值电压VT是将需要对刚刚形成良好的导电通道的栅极电压。而这个参数可以通过实验来确定，一旦设备制成，它是依赖于器件的各种材料的性能和它的值可以在制造期间被控制。
如在“定义的阈值的”所讨论的，阈值电压定义为需要生产的＆S = 2＆ f中的通道的源端的表面电位的栅极电压。
它是产生于表面上的载流子浓度在沟道等于源端，而是，在基板符号相反的栅极voltgate 。
这种表面电势是依赖于栅极和衬底上，并且氧化层的厚度之间的功函数差。除了表面电位的这些先前所讨论的原因，可能有电荷在栅极下面的材料..
3 The advantages of this structure over that of a conventional BJT are
1 The device area can be reduced compared with conventional devices.
2 The extrinsic base regions can be made short and heavily doped, reducing the base resistance
3 The intrinsic base resistance is reduced by a factor of 4 by the use of a double base.
4 The base-collector junction area can be made smaller, thus reducing the associated junction capacitance.
5 The active emitter area can be made small, reducing its junction capcacotance.
6 The polysilicon emitter can extend over an appreciably larger area than the active emitter,reducing the emitter resistance.
7 The presence of the polycrystalline portion of the emitter increases the current gain.
These transistors are designed for high speed,and they also exhibit higher-than-expected &'s. It is not well understood that the use of the polysilicon emitter structure increase &,Several models explain this effect exist,and one of these models is based on the effects of band-gap narrowing being less in polysilicon than in monocrystalline emitters. The base is doped p type ,and with Nab emitter~=10^18cm^-3, there is some band-gap narrowing in the base,raising Ev. The n+ monocrystalline emitter is diffused into the p base region and thus, in addition to the increase in Ev already present, there is an ad
ditional decrease in Ec due to donors in the emitter. The n+ polysilicon ,however , is grown on top of these structures, and so contains a negligible concentration of acceptors. Thus in the n+ polysilicon, there is only the band-gap narrowing due to the donors and Ev is not affected.
3这种结构的较常规的双极结型晶体管的优点是
1所述的装置区域可与常规器件相比减少。
2非本征基区可制成短和重掺杂，减小了基极电阻
3本征基极电阻由4倍减少通过使用双碱。
4的基极 - 集电极结区可以做得更小，从而降低了相关的结电容。
5有源发射极面积可以做得很小，降低了它的结capcacotance 。
6所述的多晶硅发射极可延伸到一个比有源发射极略微更大的面积，从而降低发射极电阻。
7发射器的多晶部分的存在增加的电流增益。
这些晶体管是专为高速，他们也表现出高于预期及的。它不能很好地理解的是，使用多晶硅发射极结构的增加及，几个模型解释这种效应存在，并且这些模型之一是基于带隙变窄即减多晶硅比单晶硅中发射极的作用。该基地是掺杂的p型，并与发射器的Nab ? = 10 ^ 18厘米^ -3 ，有一定的带隙变窄的基础上，提高Ev值。在n +单晶发射极扩散到p型基区，因此，除了增加的Ev值已经存在，存在的Ec由于在发射极献血者的额外减少。在n +多晶硅，然而，生长在这些结构的顶部，并因此包含受体的浓度可忽略不计。因此，在N +多晶硅，只有带隙变窄，由于供体和Ev值不受影响。
4 In addition to its application as an amplifier , the transistor is use as an ON-OFF switch. Driven by a current pulse waveform, the transistor is made to operate in the cutoff region and in saturation. The transistor is considered to be ON in saturation because the collector current is large and its resistance is low. It is considered to be OFF in the cutoff region since there is no current flow under this condition . In saturation, the collector current is limited by the load resistance.
The saturatin condition is satisfied if both emitter and collector junctions are forward-biased, and the cutoff condition is satiefied if both junctions are reverse-biased. The minority-carrier storage in the collector is usually small compared with the total charge storage in the base and will be neglected in our consideration. Switching between the ON and OFF state is accomplished by a change of the carrier distribution, these carrier densities cannot be changed instantaneously. The transition time from one state to the state to the other, known as the switching time, corresponds to the establishment of removal of the minority carriers involved.
4除了其作为放大器应用中，晶体管是作为一个ON-OFF开关使用。由一个电流脉冲波形，该晶体管是在截止区和饱和操作。晶
体管被认为是对在饱和度，因为集电极电流大，其电阻是低的。它被认为是关在截止区，因为有这样的条件下没有电流流过。在饱和状态时，集电极电流是由负载电阻的限制。
该saturatin条件满足，如果两个发射极和集电极结正向偏置，截止条件satiefied如果两个结被反向偏置。在收集少数载流子存储通常是很小的，总电荷存储在基比较，我们考虑将被忽略。在ON和OFF状态之间进行切换时由载流子分布的变化来实现，这些载流子密度不能瞬间改变。从一种状态过渡时间的状态到另一个，被称为开关时间，相当于建立搬迁所涉及的少数载流子的。