Method of making thin film transistors

A manufacturing method of a thin film transistor which comprises a first conductive layer composed of a conductive material selectively deposited on a transparent insulative substrate, an insulating layer covering the exposed surface of said substrate and said first conductive layer, a semiconductive layer covering a particular surface of said insulating layer, a pair of second conductive layers formed overlapping said semiconductive layer partially, and a transparent conductive layer electrically contacting with one of said second conductive layers, being characterized by

• forming a first thin film of an aluminum system metal on said transparent insulative substrate as said first conductive layer,
• forming a second thin film of a metal other than said aluminum system metal on said first conductive layer, said metal being anodic-oxidizable,
• anodic-oxidizing said thin film of a metal other than said aluminum system and part of said aluminum system metal and, thereby, forming a first insulating layer on said first conductive layer, and
• depositing a thin film of silicon nitride as a second insulating layer on said first insulating layer, said first and second insulating layers forming said insulating layer covering the exposed surface of said substrate and said first conductive layer.