THIN FILM TRANSISTOR AND LIQUID CRYSTAL DISPLAY

摘要

A high-performance thin film transistor particularly for a driving circuit part of a large-screen liquid crystal display is provided. A thin film transistor of bottom gate type free from misalignment with the gate electrode and from damage from the implantation of impurities is provided. Crystal grains in the polysilicon thin film is anisotropically grown at a specific angle with respect to the direction of the gate length. Depending on the use of the liquid crystal display, the angle of the direction of the crystal grain to that of the gate length is varied. As the means for anisotropically growing grains, the shape, energy density distribution, and direction of the scanning of the laser beam are controlled and adjusted. The bottom-gate transistor has an underlying insulating layer formed on the substrate and containing impurities. Impurities in the underlying layer are diffused into the semiconductor layer in laser-annealing the amorphous silicon.