Semiconductor device and method for manufacturing semiconductor device

A semiconductor device, comprising:

• a semiconductor layer;
• a first electrode on a first side of the semiconductor layer;
• a second electrode on a second side of the semiconductor layer;
• a plurality of trenches extending into the semiconductor layer in a first direction from the second side of the semiconductor layer and spaced from one another in a second direction intersecting the first direction, wherein
• the second electrode includes:
• a first portion separated from the semiconductor layer in the first direction,
• a second portion extending in the first direction from the first portion into the plurality of trenches, and
• a third portion extending in the first direction from the first portion into the semiconductor layer between adjacent trenches in the second direction,
• the semiconductor layer includes:
• a first semiconductor region of a first conductivity type between the first electrode and the second electrode and electrically connected to the first electrode,
• a plurality of second semiconductor regions of a second conductivity type between the first semiconductor region and the second electrode and spaced from one another in the second direction, and
• a third semiconductor region of the first conductivity type electrically connected to the second electrode and between the second semiconductor regions and the second electrode in the first direction, and
• each trench has therein:
• an insulating material,
• a first conductive portion adjacent to the first semiconductor region in the second direction, a first insulating portion of the insulating material being between the first conductive portion and the first semiconductor region in the second direction,
• a gate electrode between adjacent pairs of the second semiconductor regions in the second direction, and
• a second conductive portion between the first conductive portion and the gate electrode in the first direction, a second insulating portion of the insulating material being between the first conductive portion and the second conductive portion in the first direction,
• a third insulating portion of the insulating material is between the gate electrode and adjacent second semiconductor regions in the second direction and the first semiconductor region and the second conductive portion in the second direction, and
• a fourth insulating portion of the insulating material is between the gate electrode and the second conductive portion in the first direction.

A method of manufacturing a semiconductor device, the method comprising:

• forming a trench in a first semiconductor region of a first conductivity type, the trench extending in a first direction into the first semiconductor region from a first side;
• forming a first insulating portion on the first side and an inner wall surface of the trench;
• forming a first conductive portion in the trench on the first insulating portion;
• removing an upper portion of the first conductive portion and then forming a second insulating portion in the trench on a remaining lower portion of the first conductive portion;
• removing a part of the first insulating portion and a part of the second insulating portion from the trench to expose an upper part of the inner wall surface;
• forming a second conductive portion in the trench on an upper surface of a remaining part of the first and second insulating portions;
• oxidizing a part of the second conductive portion to form a third insulating portion on the upper part of the inner wall surface of the trench and a fourth insulating portion on an upper surface of the second conductive portion;
• forming a gate electrode in the trench on a surface of the third insulating portion and a part of the fourth insulating portion;
• forming a second semiconductor region of a second conductivity type in the first semiconductor region, the second semiconductor region being adjacent to the gate electrode via the third insulating portion in the second direction;
• and
• forming a third semiconductor region of the first conductivity type above the second semiconductor region in the first direction.