why solidify increase beyound the height I have made a normal circle and cut into half. Then with single vertex selected i just pull it out and added the solidify. As u can see my .gif file. After adding the solidify modifier the circle has got the solidify but where the point i pull there its not been perfect solidify it has been increase the height from the circle edges. Its not in the same height.
That's the way the Soldify modifier works. It basically adds thickness to faces in the direction of their normals. As you can see on the animation below, the face is extruded in the direction of its normal (the cyan line).