The monolithic integrated circuit chip was enabled by Mohamed M. Atalla's surface passivation process, which electrically stabilized silicon surfaces via thermal oxidation, making it possible to fabricate monolithic integrated circuit chips using silicon. This was the basis for the planar process, developed by Jean Hoerni at Fairchild Semiconductor in early 1959, which was critical to the invention of the monolithic integrated circuit chip. A key concept behind the monolithic IC is the principle of p–n junction isolation, which allows each transistor to operate independently despite being part of the same piece of silicon. Atalla's surface passivation process isolated individual diodes and transistors, which was extended to independent transistors on a single piece of silicon by Kurt Lehovec at Sprague Electric in 1959, and then independently by Robert Noyce at Fairchild later the same year.