Patent ID: 7727822

Claim:
A method for producing an active matrix substrate, said method comprising the steps of: (a) forming, above an insulating substrate, a layer stack which includes an operating semiconductor layer and a low resistance semiconductor layer; (b) forming a first mask pattern having an insular shape on the layer stack, the first mask pattern being a resist pattern; (c) patterning the layer stack so that the layer stack becomes insular by using the first mask pattern as an etching mask; (d) oxidizing a circumferential sidewall of the layer stack whose top surface is covered by the first mask pattern, under a condition that at least an end of the first mask pattern which end contacts the low resistance semiconductor layer is not positioned more inward than an end of the layer stack which end contacts the first mask pattern so as to form a sidewall oxidized film only on the circumferential sidewall of the layer stack; (e) removing the first mask pattern so as to form an insular layer stack in which the sidewall oxidized film is formed only on the circumferential sidewall of the layer stack; (f) forming an electrode/wiring layer on the layer stack so as to cover the layer stack, wherein the electrode/wiring layer is patterned so that a drain electrode is formed so as to surround an end of a source electrode; (g) forming a second mask pattern having a wiring shape on the electrode/wiring layer; (h) patterning the electrode/wiring layer by using the second mask pattern as an etching mask; (i) patterning a whole thickness of the low resistance semiconductor layer and a partial thickness of the operating semiconductor layer by using the second mask pattern as an etching mask so that the electrode/wiring layer in a region where the insular operating semiconductor layer is formed has a same shape as the low resistance semiconductor layer; and (j) removing the second mask pattern so as to leave the low resistance semiconductor layer which has been divided on the operating semiconductor layer and the electrode/wring layer which has been electrically connected with the low resistance semiconductor layer; wherein in step (d), the sidewall oxidized film is formed only on the circumferential sidewall of the layer stack by oxidizing the circumferential sidewall of the layer stack whose top surface is covered by the first mask pattern through oxidization with ozone water or oxidization at high pressure under a condition where the end of the first mask pattern is not positioned more inward than an end of the low resistance semiconductor layer.