本篇論文中,我們藉由加入離子衝撞游離模型於三維元件模擬器內,來模擬半導體元件內部載子雪崩崩潰之現象。首先我們利用Poisson’s equation 和電子與電洞的連續性方程式,模擬三維半導體元件的載子產生與復合特性。接著我們再討論整體三維模擬器的程式流程還有帶寬(BW)的原理。再者為了實現三維模擬器讓時間更有效率,敘述如何選擇整體參數設定,緊接著討論三維在二維上的驗證。最後再顯示出三維模擬器的崩潰結果。確定無誤後,接著我們繼續探討不同擴散半徑對於崩潰電壓的影響。 In this thesis, we design a 3-D device simulator which includes the impact-ionization model to simulate the breakdown phenomenon of avalanche. First, we use Poisson’s equation, electron continuity equation and hole continuity equation to simulate 3-D device recombination rate and generation rate, and then we discuss the theorems, which include 3-D device simulator program flow chart and Band-Width property. In order to optimize efficiency in 3-D device simulation, we describe how to choose simulation parameters. After that, we discuss to prove 3-D device on 2-D stage. Finally, show the breakdown result of 3-D device simulator. After confirmation, we discuss the breakdown voltage effect on different diffusion radii.