1. A method for fabricating a semiconductor device including transistors, each having a gate electrode, a source/drain region, and a channel region on a substrate, the method comprising: first, patterning a semiconductor film on the substrate to form element regions, each to be provided with the source/drain region and the channel region, the first patterning step including: forming a second photosensitive film on the semiconductor film using a photosensitive material, exposing the second photosensitive film through a first projection exposure mask using a stepper or a scanner, the first projection exposure mask having an exposure pattern corresponding to the element regions and an exposure pattern corresponding to a first alignment mark used for alignment of a holographic exposure mask, developing the exposed second photosensitive film and removing the second photosensitive film excluding areas corresponding to the element regions and an area corresponding to the first alignment mark, and etching the conductive film through the second photosensitive film, as a mask, remaining on the semiconductor film to form the element regions and the first alignment mark; second, forming a gate insulating film covering segments of the patterned semiconductor film in the respective element regions; third, forming the gate electrodes on the gate insulating film at predetermined positions; and fourth, forming the source/drain region and the channel region in each of the element regions, the gate electrodes being formed by a process including an exposure step through the holographic exposure mask in the third step and the source/drain regions and the channel regions being formed by a process including an exposure step through a projection exposure mask using a stepper or a scanner in the fourth step.