Semiconductor device

A semiconductor device comprising:

• a single-crystal semiconductor substrate with an upper surface including a first direction in which an inverted mesa step extends and a second direction in which a forward mesa step extends in response to anisotropic etching having an etching rate depending on crystal plane orientation;
• a first bipolar transistor including a first collector layer, a first base layer, and a first emitter layer, wherein the first collector layer, the first base layer, and the first emitter layer are epitaxially grown on the semiconductor layer;
• and
• a first base wire connected to the first base layer, wherein:
• a step is provided at an edge of the first base layer,
• the first base wire is extended from inside to outside of the first base layer in a direction intersecting with the first direction in a plan view, and
• an intersection of the edge of the first base layer and the first base wire has a disconnection prevention structure making it difficult for step-caused disconnection of the first base wire to occur, compared with a structure in which an inverted mesa step formed by anisotropic etching of the first base layer and the first collector layer intersects with the first base layer.