PURPOSE: To reduce the number of photomasks to be used and to improve yield by making use of four photomasks enough for a lithography process by each specified patterning from a first stage to a fourth stage.

CONSTITUTION: A first photomask is used when a gate electrode 22 and a gate bus line 23 are used. A second photomask is used when a semiconductor film 25 which becomes an active layer of a transistor is patterned on the gate electrode 22. A third photomask is used when a picture element electrode 31, a source electrode 28, a drain electrode 29, a drain bus line 30 and a drain bus terminal part are formed. A fourth photomask is used when a film on the picture element electrode 31, the drian bus line terminal part and a gate bus terminal part is removed. Four photomasks are enough for patternings from a first stage to a fourth stage.