Simplified method of making active matrix liquid crystal display

Claim 1

A three mask method of fabricating an inverted staggered thin film transistor of an inverted staggered structure for active matrix crystal display systems with a matrix of picture elements, each thin film transistor having a gate, a source, and a drain, comprising the steps of: depositing a metal film on a transparent substrate; patterning said metal film as said gate electrode of said thin film transistor, as scan lines, and as data lines using a first mask; successively depositing an insulating layer, an amorphous semiconductor layer, and a heavily doped amorphous semiconductor layer over said transparent substrate; simultaneously patterning said insulating layer, said amorphous semiconductor layer, and said heavily doped amorphous semiconductor layer using a second mask to form a mesa; depositing a transparent conducting layer over said mesa; and patterning said transparent conducting layer using a third mask to form electrodes of picture elements, and crossover connections of said data lines at cross-points with said scan lines.