Electron source, electron beam device, and method for manufacturing electron source

A method for manufacturing an electron source, the electron source including a tip substrate that includes a protrusion configured to emit an electron when an electric field is generated, a shank that supports the protrusion and has a diameter decreasing toward the protrusion, and a body that supports the shank, wherein the protrusion, the shank, and the body are each made of a hexaboride single crystal, the method comprising:

• a step of forming a mask on the protrusion of the tip substrate;
• a step of forming, on a part of the tip substrate including the shank and the body but excluding the protrusion, a material having a work function larger than that of the hexaboride single crystal;
• and
• a step of removing the mask to expose the protrusion;
• wherein the protrusion includes a tip having a curvature radius of 0.2 μm or more and 0.5 μm or less,
• a length of the protrusion is 5 μm or more and 20 μm or less,
• and a thickness of a covering film of the material formed on the part including the shank and the body but excluding the protrusion is 1 μm.