Higher quality polycrystalline silicon thin films exhibited higher electron mobility and were usefu for transistors for active-matrix flat-panel displays. The better compatibility with the peripheral circuits in an additional advantage in an integrated system. Several techniques have been employed to enhance the crystal quality of low temperature grown amorphous silicon, such as solid phase crystallization, excimer laser annealing, and metal-induced lateral crystallization. In this paper, we present a modified crystallization process using current-induced joule heating under vacuum. A thin layer of high temperature resistant tungsten was sputtered on the amorphous silicon as the conducting medium and metal seed. The thin film thickness was measured by α-stepper. The high current density provided effective means in crystallizing the amorphous silicon layer. The crystalline morphology was studied by scanning electron microscopy (SEM) after secco-etch, transmission electron microscopy (TEM) and x-ray diffraction (XRD), under different annealing conditions. The grain size has been in the range of 0.1-1 μm and could be increased with annealing time. No tungsten silicide was observed. Some defects were formed due to the electron-migration effect. In addition, a heating profile due to current distribution would be proposed.