A liquid crystal display device using a plastic substrate becomes required to have high resolution, high opening ratio, high reliability, or the like, with the increasing of a screen size. Besides, high productivity and cost reduction is also required. According to the present invention, a protective film 123 comprising at least one silicon nitride film, which is formed by a ratio frequency sputtering using a silicon target, is provided over an opposing substrate (a flexible substrate); sealant 112 is drawn; a liquid crystal material 114 is dropped over the opposing substrate in vacuo; and the opposing substrate is pasted to a flexible substrate 110 provided with a pixel electrode 111 and a columnar spacer 115.