中文摘要：

以BSIM4模型为基础,从沟道电荷密度、有效源漏电压、载流子速度饱和及阈值电压等几个方面出发,找出BSIM4模型中导致不对称的因素,给出了对称的沟道电荷密度公式、源漏有效电压公式和载流子速度饱和公式;同时通过在源端和漏端分别计算的方法,抵消源/漏电压处理方式不同所带来的不对称性;最后推导出新的对称的沟道电流公式.模型验证表明：改进后的模型不但可以准确地模拟器件的特性,而且拥有更高的对称性.改进模型拓宽了BSIM4模型的运用范围,可以更有效地运用于RF集成电路设计和仿真.

英文摘要：

On the basis of BSIM4（Berkeley short-channel IGFET model 4）model,the asymmetry in the BSIM4 models was analyzed.From some aspects,including the channel charge density,effective source-drain voltage,carrier saturation velocity and threshold voltage,the factors that lead to the asymmetry in the BSIM4 models were identified,and the symmetric channel charge density formula,effective source-drain voltage formula,carrier saturation velocity formula were developed.By calculating in the source side and drain side respectively,the asymmetry due to the unparallel dealing with the source voltage and the drain voltage was eliminated.Finally,symmetrical channel current formula was deduced.It is verified that the improved model not only simulates devices accurately,but also is more symmetric.The improved model expands the application scope of the BSIM4 models which can be applied efficiently in the RF（radio frequency）design and simulation.