Thin film transistor and preparation method

A preparation method of a thin film transistor comprises the steps of forming a grid metal layer on a semiconductor layer; forming a photoresist layer on the grid metal layer; and enabling the grid metal layer to be formed into a pseudo-grid through a composition process; taking the pseudo-grid as a mask; performing a heavy doping ion implantation technology on the semiconductor layer, and forming a source heavily doped region and a drain heavily doped region; performing ashing process on the photoresist layer on the pseudo-grid, so that the size of the photoresist layer is same with that of the grid to be formed; etching an area which is not covered by the photoresist layer on the pseudo-grid, and forming the grid; taking the grid as a mask; performing lightly doped ion implantation process on the semiconductor layer, and forming a source lightly doped region and a drain lightly doped region. According to the preparation method of the thin film transistor, a patterning process for one time is only needed, then the production of the drain heavily doped region, the grid, and the drain lightly doped region can be realized, compared with a conventional process, the process cost is reduced, and the process time is shortened.