Double gate static induction thyristor

Claim 1

A double gate static induction thyristor comprising a semiconductor substrate having first and second principal surfaces opposite to each other, a first gate region formed at the first principal surface of the semiconductor substrate, a first semiconductor region of a first conduction type formed on the first principal surface of the semiconductor substrate, a second gate region formed at the second principal surface of the semiconductor substrate, a second semiconductor region of a second conduction type opposite to the first conduction type and formed on the second principal surface of the semiconductor substrate, gate electrodes formed on the first and second gate regions, and main electrodes formed on the first and second semiconductor regions, portions of the semiconductor regions surrounded by the gate region forming a current path between the main electrodes, wherein the improvement is that each of the first and second gate regions has a first diffusion region positioned underneath the corresponding gate electrode in ohmic contact with the corresponding gate electrode, and a second diffusion region which extends from the first diffusion region toward a semiconductor region of the semiconductor substrate positioned between the main electrodes, a large part of the second diffusion regions is spaced away from the first diffusion region in a cross-sectional view along the direction of the current flow between said main electrodes, and is electrically connected to the first diffusion region, a diffusion depth of the first diffusion region from the surface in contact with the corresponding gate electrode being larger than that of the second diffusion region from the same level as the surface of the first diffusion region in contact with the corresponding gate electrode.