Patent ID: 7009239

Claim:
A vertical semiconductor device comprising: a semiconductor substrate of a first conductivity type including a first main surface and a second main surface opposed to said first main surface, said semiconductor substrate including an element region and a peripheral provided so as to surround said element region; a first impurity region of a second conductivity type having a higher impurity concentration than said first conductivity type of said semiconductor substrate, formed inside said semiconductor substrate so as to be exposed at said second main surface; a trench provided in said peripheral region and having an almost vertical sidewall with reference to said first main surface; and a second impurity region of said second conductivity type formed along said sidewall of said trench inside of said semiconductor substrate in a prescribed thickness and electrically connected to said first impurity region, wherein a ratio d/w (aspect ratio) between a depth d and an opening width w of said trench is 5 or more and 100 or less.