Semiconductor device and manufacturing method of semiconductor device

A method of manufacturing a semiconductor device, comprising:

• epitaxially forming a base region with a second conduction type on a drift region with a first conduction type;
• forming a mesa region between at least two isolation trench portions, by partially etching the drift region and the base region;
• epitaxially forming a contact layer that contacts a top portion of the mesa region, side portions of the mesa region, and bottom portions of the isolation trench portions, has an opening on the source region, has a position of an end portion of the opening that matches a position of a side end portion of the source region in a top view of the semiconductor device, and has a second-conduction-type impurity concentration that is higher than that of the base region;
• and
• forming a gate trench portion.

A method of manufacturing a semiconductor device, comprising:

• epitaxially forming a base region with a second conduction type on a drift region with a first conduction type;
• forming a mesa region between at least two isolation trench portions, by partially etching the drift region and the base region;
• epitaxially forming a contact layer that contacts a top portion of the mesa region, side portions of the mesa region, and bottom portions of the isolation trench portions, and has a second-conduction-type impurity concentration that is higher than that of the base region;
• and
• forming a gate trench portion, wherein
• the epitaxially forming the contact layer is performed after the forming the mesa region and before the forming the gate trench portion, and the method of manufacturing the semiconductor device further comprises:
• thermally treating the contact layer, after the epitaxially forming the contact layer and before the forming the gate trench portion;
• forming an opening in the contact layer, after the thermally treating the contact layer and before the forming the gate trench portion;
• and
• ion-implanting impurities with a first conduction type in the base region via at least the opening, after the forming the opening in the contact layer and before the forming the gate trench portion.