Liquid discharge head substrate and liquid discharge head

Performing a high-speed recording operation using a slender liquid discharge head substrate causes an uneven temperature distribution for each energy generating element because the center portion of the liquid discharge head substrate is more liable to accumulate heat than the end portion thereof, which may affect the quality of a recorded image. For this reason, the surface of the energy generating element which contacts liquid is separated into a first region and a second region in which a protection film is thicker than the one in the first region, and the area in the first region for the element positioned at the end portion of the array of the elements is made greater than that in the first region at the center portion thereof.