This study reports our two unpredictable behaviors for fracture of nano-scale silicon with 100 nm thickness. We developed a novel tensile testing method conducted on silicon chip to observe a local area in large magnified view during tensile test. For comparing fracture behavior of 100 nm-thick silicon film with V-notch and U-notch, we performed FEM analysis to optimize the locations of notches. The results shows that V-notch generating large local stress-field at a notch root was stronger for tensile stress than U-notch.