Diffusion Transistor - Planar Transistor

The planar transistor was developed by Dr. Jean Hoerni at Fairchild Semiconductor in 1959. The planar process used to make these transistors made mass produced monolithic integrated circuits possible.

These transistors have a silica passivation layer to protect the junction edges from contamination, making inexpensive plastic packaging possible without risking degradation of the transistor's characteristics over time.

The first planar transistors had much worse characteristics than alloy junction transistors of the period, but as they could be mass produced and alloy junction transistors could not, they cost much less and the characteristics of planar transistors improved very rapidly, quickly exceeding those of all earlier transistors and making earlier transistors obsolete.