Heater

1. A heater comprising:

a ceramic structure;

a heat-generating resistor embedded in the ceramic structure;

a conductor line embedded in the ceramic structure so as to be connected to the heat-generating resistor;

a through-hole conductor disposed in the ceramic structure, one end of the through-hole conductor being connected to the conductor line and the other end of the through-hole conductor being led out to a surface of the ceramic structure; and

an electrode pad disposed on the surface of the ceramic structure so as to cover the through-hole conductor, the electrode pad being connected to the through-hole conductor, the electrode pad having a recess,

the through-hole conductor having a protrusion which protrudes outwardly beyond the surface of the ceramic structure, the protrusion having a portion extending in the recess, the portion extending in the recess of the protrusion being closely covered with the electrode pad.

2. The heater according to claim 1 ,

wherein the protrusion has a curved surface.

3. The heater according to claim 1 ,

wherein the one end of the through-hole conductor is buried into the conductor line.

4. The heater according to claim 3 ,

wherein the one end of the through-hole conductor connected to the conductor line has a curved surface.

5. The heater according to claim 1 ,

wherein the protrusion is composed of a plurality of convexities.

6. The heater according to claim 1 ,

wherein the through-hole conductor is cylindrically shaped.

7. The heater according to claim 1 ,

wherein the portion extending in the recess of the protrusion has a portion which widens gradually as the protrusion extends into the recess.

8. The heater according to claim 1 ,

wherein the protrusion has a recess and the electrode pad extends in the recess of the protrusion.