Semiconductor device with an extended base region

A semiconductor device according to the present invention includes: a first region (11) having a first conductive type; a plurality of second regions (17) having a second conductive type that differs from the first conductive type, and arranged in the first region; a plurality of third regions (19) having the first conductive type and formed in the second regions; an electrode (12) for forming a channel between the first region and the third region; and a plurality of extended second regions (20) having the second conductive type, arranged in the first region (11) such as to individually include one of the second regions (17) and having an impurity density that is lower than an impunity density of the second regions (17). In embodiments an extended second region (113) extends between the first region (101) and the second regions (102) so as to fully cover said first region (101).