PURPOSE: To prevent disconnection of an upper electrode by making a lower electrode in a step-like cross section in manufacture of an active matrix substrate composed of a reverse-stagger type thin film transistor array.

CONSTITUTION: A conductive film 2 is formed on an insulating substrate 1, and a photoresist 3 is applied thereon. The photoresist 3 is then exposed to light to form a latent image, and first development is carried out with a developer solution to form a resist pattern. The lower conductive film is patterned. Then, another development is carried out with the developer solution to over-develop the photoresist pattern. Using this over-developed resist pattern 3, the conductive film 2 is etched to approximately half the thickness thereof. Then, the resist pattern is removed, and a gate electrode of an active matrix substrate is formed in a step-like shape.