There are provided a structure of a semiconductor device in which low power consumption is realized even in a case where a size of a display region is increased to be a large size screen and a manufacturing method thereof. A gate electrode in a pixel portion is formed as a three layered structure of a material film containing mainly W, a material film containing mainly Al, and a material film containing mainly Ti to reduce a wiring resistance. A wiring is etched using an IPC etching apparatus. The gate electrode has a taper shape and the width of a region which becomes the taper shape is set to be 1 .mu.m or more.