Method of forming insulator of selectively varying thickness on patterned conductive layer

Claim 1

A manufacturing method in which: a body is provided with a patterned first electrically conductive layer having a portion protruding upward beyond adjacent parts of the conductive layer; and an electrically insulating layer is formed on the conductive layer and on adjacent parts of the body such that a portion of the insulating layer protrudes upward beyond adjacent parts of the insulating layer generally at the location above the protruding portion of the conductive layer; characterized by the steps of: forming on the insulating layer a further layer having a generally planar upper surface; exposing at least part of the protruding portion of insulating layer by etching the further layer with a first etchant that attacks material of the further layer much more than material of the insulating layer; and etching the remainder of the further layer and the insulating layer as it becomes exposed with a second etchant that attacks material of the insulating and further layers at rates not substantially different from each other.