Abstract: The disclosed is a semiconductor device which comprises a circuit which is formed on a substrate and which includes an insulated gate type semiconductor field-effect transistor element or an TFT element, wherein as compared with the electrostatic capacitance per a unit area of a gate insulating film at a channel part of the transistor element, the electrostatic capacitance per a unit area of a insulating film at the other portion of overlap part between electrodes or wiring lines is small. In the semiconductor device which has an insulated gate type semiconductor field-effect transistor element or a TFT element, a high mutual conductance is obtained and the absolute value of gate threshold voltage is repressed while the adverse influence to the circuit operation by means of the parasitic capacity is repressed.