Two of the world’s largest manufacturers of the machinery used to produce semiconductors, Applied Materials of Santa Clara and Tokyo Electron of Japan, on Monday dropped plans to merge after the Justice Department said that combining their businesses would restrict competition. Microchip factories are becoming increasingly large and costly to build, even as prices for the tiny chips they produce are steadily tumbling. Pressure on suppliers of chip-making machinery is intense, and the industry has consolidated into a clique of large, technically sophisticated groups. By joining forces, Applied Materials and Tokyo Electron had hoped to streamline research and development operations and benefit from greater manufacturing scale. Mylan N.V.