A method decreases the time and cost for producing an active matrix substrate of a liquid crystal display device. The method includes steps of forming patterns for scanning lines, separating silicon elements for thin film transistors from a semiconductor layer, forming video signal lines and liquid crystal drive electrodes at the same time, forming spacer bumps or spacers and insulation bumps at the same time via a halftone exposure process thereby creating a taper angle of less than 30 degrees at each edge of the bump, forming contact holes, and forming transparent common electrodes for shielding the video signal line and transparent common electrodes within pixels at the same time. The halftone exposure process utilizes a light transmission adjustable photomask having a translucent area or conducts a two-step exposure process by utilizing a normal photomask.