Method for adjusting groove depth and method for manufacturing semiconductor device

A method for manufacturing a semiconductor device, comprising:

• obtaining a first width of a trench which implements an insulated gate structure arranged in an active area and a second width of a mesa-groove which is arranged so as to surround the active portion in an outer-edge area, the second width being wider than the first width;
• acquiring a mask thickness capable of etching the trench having the first width and the mesa-groove having the second width to the same depth by:
• preparing masks having different thicknesses on respective top surfaces of a plurality of substrates made of silicon carbide,
• forming a first opening having a predetermined width and a second opening having a width wider than the first opening in each of the masks,
• simultaneously forming a first groove and a second groove in each of the substrates by selectively etching via the first opening and the second opening,
• measuring a depth ratio of the first groove to the second groove in each of the substrates, and
• acquiring a thickness of a mask such that the depth ratio is an intended value, from a relationship between each thickness of the masks and each depth ratio in the substrate;
• forming a base region of a second conductive type on a top surface of a drift region of a first conductive type in a target substrate made of silicon carbide;
• selectively forming a source region of the first conductive type having a higher impurity concentration than the drift region in an upper portion of the base region;
• depositing a target mask on top surfaces of the source region and the base region with the mask thickness;
• forming a first opening having the first width and a second opening having the second width in the target mask;
• simultaneously forming the trench and the mesa-groove in the target substrate by selectively etching via the first opening and the second opening;
• and
• forming an insulated-gate electrode structure in the trench.