Semiconductor device, and method for manufacturing semiconductor device

A semiconductor device comprising:

• a first conductive-type SiC semiconductor layer having a front surface, a back surface and end surfaces surrounding the front surface and the back surface, the SiC semiconductor layer having a semiconductor element structure at a side of the front surface;
• a first insulating layer formed at a side of the front surface of the SiC semiconductor layer;
• a surface electrode connected to the front surface through the first insulating layer;
• a second insulating layer having an opening from which a part of the surface electrode is exposed such that the second insulating layer covers another part of the surface electrode and the first insulating layer, the second insulating layer reaching the end surface of the SiC semiconductor layer;
• and
• a rear electrode formed on the back surface of the SiC semiconductor layer, wherein
• the second insulating layer extends horizontally from the end surface of the SiC semiconductor layer to the surface electrode in a cross section such that the second insulating layer has a flat top portion,
• a portion of the second insulating layer covering an upper part of the surface electrode is thinner than a portion of the second insulating layer covering another part of the surface electrode in a cross section,
• the semiconductor element structure includes a Schottky barrier diode structure such that the surface electrode is made of a material forming a Schottky barrier between the SiC semiconductor layer and the surface electrode or an MIS transistor structure having a source electrode as the surface electrode,
• an outer edge portion of the surface electrode, an inner edge portion of the first insulating layer and an inner edge of the second insulating layer are arranged in this order from the end surface of the SiC semiconductor layer, and
• when a potential difference of 1000 V or more which is equal to or greater than a maximum applied voltage of the semiconductor element structure is generated between the surface electrode and the SiC semiconductor layer, a distance X1 (μm) from an edge of the opening in the second insulating layer to the end surface of the SiC semiconductor layer satisfies the following relational expression (1):
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A method for manufacturing a semiconductor device, comprising:

• preparing an SiC wafer including a first conductivity-type SiC substrate and a first conductivity-type SiC epitaxial layer formed on the SiC substrate;
• defining an element region in which a plurality of semiconductor devices are formed and a dicing region that demarcates the element region and end surfaces of the plurality of semiconductor devices that are separated from each other after singulation;
• forming a first insulating layer in a predetermined area on a front surface of the SiC epitaxial layer in each the element region;
• forming a contact hole from which the front surface of the SiC epitaxial layer is selectively exposed in each the element region;
• forming a surface electrode in the contact hole in each the element region so as to be connected to the front surface of the SiC epitaxial layer;
• forming a second insulating layer on the first insulating layer so as to cover each the element region and a periphery of the surface electrode;
• and
• dicing the SiC wafer by cutting along the dicing region so as to form end surfaces of the SiC substrate and the SiC epitaxial layer and the end surface of the second insulating layer simultaneously flush with each other in each the semiconductor device, wherein
• the second insulating layer extends horizontally from the end surface of the SiC semiconductor layer to the surface electrode in a cross section such that the second insulating layer has a flat top portion,
• a portion of the second insulating layer covering an upper part of the surface electrode is thinner than a portion of the second insulating layer covering another part of the surface electrode in a cross section, and an outer edge portion of the surface electrode, an inner edge portion of the first insulating layer and an inner edge of the second insulating layer are arranged in this order from the end surface of the SiC semiconductor layer.