PURPOSE: To eliminate the variability of a parasitic capacity by providing two source electrodes and drain electrodes wired in parallel in a predetermined length with a predetermined line width, and a gate electrode provided on a semiconductor layer provided in a direction crossing the longitudinal direction.

CONSTITUTION: Two source electrodes 103 are so provided as to be parallel to each other. Drain electrodes 102 are so provided of the same material as that of the source electrodes between the electrodes 103 as to be parallel to the electrodes 103. A gate electrode 106 covers a semiconductor layer 104 through a gate insulating film 105. The film 105 is used also as an interlayer insulating film for holding insulation between the wirings. The channel length L of a thin film transistor is as designated by arrows 109, the interval of the parallel electrodes 103 is the sum of twice as large as the length L and the line width of the electrodes 102. Its channel width W is twice as large as the value designated by arrows 110. Even if the pattern is displaced in any direction, the parasitic capacity of a thin film transistor becomes always constant.