Method for fabricating semiconductor device with oxide semiconductor material

Abstract

A method of making a semiconductor device that includes forming a vertical access transistor including forming bit lines in a first direction on a substrate, forming a polysilicon pillar as a sacrificial pillar over each bit line of the bit lines, forming a gate oxide on side surfaces of the polysilicon pillar, forming a word line, in a second direction, on the polysilicon pillar with the gate oxide interposed between the word line and the polysilicon pillar, the second direction being not substantially parallel to the first direction, after forming the word line, removing the polysilicon pillar so as to leave a vertical void in place of the polysilicon pillar, filling the vertical void with an oxide semiconductor that serves as a channel for the vertical access transistor; and forming a cell capacitor over the channel of the vertical access transistor.