由於金屬氧化物薄膜電晶體獨特的製程特質及材料特性，使它們在新興的薄膜電晶體應用上成為最具有競爭性的選擇，包含均勻性好可以應用在大尺寸的面板、低溫製程而應用於可撓式的結構以及低成本製作等特殊需求的產品上。為了尋求更好的TFT效能，我們將使用高介電常數(High-k)材料二氧化鉿(HfO2)來製備元件之閘極絕緣層(Gate Insulator)並且在本論文中研究及評估以HfO2替代SiO2作為閘極絕緣層之可行性。
首先，我們利用金屬遮罩(Shadow Mask)製作MIM電容以及IGZO-TFT元件，測試HfO2在不同的通氧比例〔O2/(Ar+O2)〕下對薄膜特性以及運用在TFT元件之閘極絕緣層上電特性的影響，依序利用AFM、SEM和C-V量測…等探討其表面粗糙度、介電常數、絕緣能力以及TFT元件電特性結果，發現HfO2薄膜在通氧比例為33%時有最佳的元件電特性。接著，我們利用微影(Photolithography)製程製作小尺寸的TFT元件並同時探討不同通道長度元件的電特性變化、元件閘極經圖案化後對電特性的影響、針對不同通道長度的元件可靠度研究以及電特性的表現均勻度，最後，我們將和在相同製程下以SiO2當作閘極絕緣層之元件及其他同樣使用HfO2當作閘極絕緣層之IGZO-TFT的文獻做電特性的總比較。

Metal oxide semiconductor is considered to be the most competitive TFT material for last decade. It has several advantages such as great uniformity for large size display, low fabrication temperature and low production cost. In order to pursue greater metal oxide TFT performance, high-k dielectric was introduced as a gate insulator in TFT structure. Among all high-k dielectrics, HfO2 is well known for its high dielectric constant and large band gap. Therefore, we will focus on evaluating the basic properties and electrical characteristic of HfO2 as a gate insulator in this study.
To begin with, we fabricated MIM capacitor and IGZO based TFT whose dielectric layer was deposited in different〔O2/ (Ar+O2)〕ratio through shadow mask technique. Next, the roughness and the thickness of HfO2 dielectric layer were demonstrated by AFM and SEM. We discovered that HfO2 film with 33% oxygen pressure ratio has the greatest gate insulator properties due to its roughness, dielectric constant and resistivity. In order to reduce the off current of TFT device, photolithography technology and HfO2 film with 33% oxygen pressure ratio were utilized to fabricate smaller size TFT device. A series of measurements were performed for different channel length of devices including Hystersis, PGBS, NGBS, PGDBS and NGDB. Overall, several comparisons had been made between our device and device which was fabricated in same process but has different gate insulator.

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