Semiconductor device including a semi-insulating layer contacting a first region at a first surface of a semiconductor layer

A semiconductor device, comprising:

• a first electrode;
• a first semiconductor region of a first conductivity type on the first electrode;
• a second semiconductor region of a second conductivity type on the first semiconductor region;
• a second electrode on a first surface of the second semiconductor region, the first and second semiconductor regions being between the first and second electrodes in a first direction;
• a third semiconductor region of the second conductivity type on the first semiconductor region and adjacent to second semiconductor region in a second direction intersecting the first direction, an impurity concentration of the third semiconductor region being less than that of the second semiconductor region;
• a fourth semiconductor region of the first conductivity type on the first semiconductor region, a portion of the first semiconductor region being between third and the fourth semiconductor regions in the second direction, an impurity concentration of the fourth semiconductor region being greater than that of the first semiconductor region;
• a third electrode contacting the fourth semiconductor region;
• a first insulating layer on the third semiconductor region, the first insulating layer surrounding a first portion of the second electrode in a first plane parallel to the first surface, a second portion of the second electrode being above the first insulating layer in the first direction, an outer edge of the first insulating layer extending in the second direction beyond an outer edge of the second portion of the second electrode;
• and
• a semi-insulating layer contacting the second electrode, the first insulating layer, the third semiconductor region, the first semiconductor region, and the third electrode, a portion of the semi-insulating layer being between the outer edge of the first insulating layer and the third semiconductor region in the first direction.

A semiconductor device, comprising:

• a first electrode;
• a semiconductor layer on the first electrode and including:
• a first region of a first conductivity type electrically connected to the first electrode;
• a second region of a second conductivity type on the first region at a first surface of the semiconductor layer;
• a third region of the second conductivity type at the first surface and contacting the second region, the third region surrounding the second region in a first plane parallel to the first surface and having an impurity concentration less than that of the second region;
• a fourth region of the first conductivity type at the first surface and surrounding the third region in the first plane, the fourth region being spaced from the third region in a first direction that is parallel to the first plane and having an impurity concentration greater than that of the first region;
• and
• a plurality of fifth regions of the first conductivity type on the second region spaced from one another in the first direction;
• a second electrode electrically connected to the second region, the second electrode including a first portion above the second region in a second direction that is orthogonal to the first plane and a second portion surrounding the first portion in a second plane parallel to the first plane;
• a plurality of gate electrodes below the second electrode in the second direction, each gate electrode contacting the first region, the second region, and the fifth region via a gate insulating layer;
• a third electrode on the first surface and surrounding the second electrode in the second plane, the third electrode being spaced from the second electrode in the first direction and electrically connected to the fourth region;
• a semi-insulating layer contacting the first region at the first surface between the third and fourth regions, the semi-insulating layer contacting the second electrode and the third electrode;
• and
• a first insulating layer between the second portion and the third region in the second direction and contacting the first surface, a first end portion of the first insulating layer that is spaced from the second electrode in the first direction towards the third electrode is above the third region in the second direction, wherein
• the fifth regions are each electrically connected to the second electrode by contact plugs extending through the first insulating film.