Method of making nonvolatile memory elements with selector transistors

A method of manufacturing a semiconductor memory including a plurality of memory elements arranged in a matrix formation on a semiconductor substrate, each memory element having a floating gate and a control gate, and selector transistors, each provided with a gate, for selecting said memory elements, comprising the steps of:

• forming a floating-gate conductive layer, an intergate insulating layer, and a control-gate conductive layer on a semiconductor substrate, including a memory element region portion and a selector transistor region portion in each active region of said semiconductor substrate;
• in conjunction with patterning of control gates forming each word line by preferential etching of said control-gate conductive layers, said intergate insulating film, and said floating-gate conductive layers, forming a first contact hole passing through said control-gate conductive layer and opening above said intergate insulating layer in that portion of said control gate which is close to each said selector transistor region portion;
• forming source and drain regions in each said memory element region portion and in each said selector transistor region portion;
• after covering the surface of said substrate with an interlayer insulating film, forming a drain contact hole passing through said interlayer insulating film and opening to each said drain region, and simultaneously forming a second contact hole passing through said first contact hole portion and said intergate insulating layer and opening to each said floating-gate conductive layer;
• and
• forming bit lines each passing through said drain contact hole and contacting to said drain region, and simultaneously forming a connector passing through said first and second contact holes and connecting said floating-gate conductive layer and said control-gate conductive layer together in each selector transistor.