近年來由於元件的尺寸越縮越小，操作電壓卻沒辦法有相當幅度的減降，而造成不容小覷的橫向電場，因此熱載子效應對於半導體元件而言已經成為一項不可忽視的問題。
進一步而言在基板電流所發現產生的新現象，有別於以往基板電流的單一峰值，後面又接著發生第二個峰值的現象也逐漸的被探索研究當中。在本文中是以0.6um，BCD製程，操作電壓為15伏特的橫向擴散金氧半場效電晶體（LDMOSFET）去研究與分析其基板電流的行為現象，解釋為何會出現此現象，結構的改變對其基板電流又有何影響，並予以Tsuprem4與Medici等模擬軟體去輔助驗證結果。
在本文的最後去探討此種基板電流現象對於整個元件的行為特性而言究竟是優點抑或是缺點，並且去討論可以改善此元件的方法，使的往後在設計與分析元件行為時有個理論依據。

In recent years, device has become smaller gradually. Due to the reason the problem of hot-carrier effect becomes more and more important. So in this thesis we study the substrate current and reliability of LDMOSFET.
In this thesis we use the BCD 0.6um process and the operate voltage on drain and gate are both 15 volts. We find a new phenomenon of substrate current. There is a second substrate current hump (SSCH) appears. We use TCAD (Tsuprem4 and Medici) to understand and analysis the strange phenomenon.
At last we judge the effect of SSCH in this device and try to improve the performance. In this thesis we make a basic theory of the substrate current.

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