 The static induction transistor, the first high frequency transistor concept, was invented by Japanese engineers Jun-ichi Nishizawa and Y. Watanabe in 1950, and was finally able to produce some experimental prototypes in 1975.Further developments included the grown-junction transistor (1951), the surface-barrier transistor (1953), the diffusion transistor, the tetrode transistor, and the pentode transistor.The diffused silicon 'mesa transistor' was developed at Bell in 1955 and made commercially available by Fairchild Semiconductor in 1958.