Name Hitachis Early Vmos Commercialization

# Name Hitachi's Early VMOS Commercialization

## 7. Name Hitachi's Early VMOS Commercialization

Hitachi was among the first manufacturers to commercialize a vertical power MOSFET structure, bringing V-groove and vertical double-diffused parts to market in the mid-1970s aimed squarely at audio-amplifier and early switching applications where bipolar transistors' switching speed and drive complexity were becoming limiting factors. Hitachi's early vertical MOSFET work used a V-shaped groove etched into the silicon to help define the vertical current path — a related but distinct geometric approach from the planar double-diffused cell structure described in step 2, both converging on the same goal of a vertical, voltage-controlled power switch.

Hitachi marketed these early devices partly on their fast switching speed and partly on audio linearity advantages relevant to amplifier applications, a market where MOSFETs' absence of minority-carrier storage time gave them a distinctly different, often preferred, sonic behavior compared to bipolar output stages. This is named here as one of three early, independently pursued commercial efforts — alongside Siliconix (step 9) and International Rectifier (step 8) — that together established vertical power MOSFETs as a viable commercial product category within a few years of each other.