ACTIVE MATRIX SUBSTRATE

摘要

PURPOSE:To obtain a high-quality display whose unevenness in a contrast at an upper part and a lower part is small and whose unevenness in a contrast at each pixel is small by a method wherein a groove is made in an insulating substrate and pixel-adding capacitance is constituted inside the groove in order to obtain a retention characteristic of a sufficient pixel potential. CONSTITUTION:A groove 11 is made in an insulating substrate. For this operation, an ordinary isotropic etching operation may be used; however, when a deep and narrow groove is to be formed, it is sufficient to execute a dry isotropic etching operation. Then, a first polycrystalline silicon thin film 12 which has been doped with an impurity is deposited; while the film inside the groove 11 and a common line 6 are left, the film in other parts is removed by a patterning operation. Then, the polycrystalline silicon thin film 12 is thermally oxidized; an insulating oxide film 13 for pixel-adding capacitance use is formed; after that, a second polycrystalline silicon thin film 14 which has been doped with an impurity is deposited in order to fill the inside of the groove 11. Then, a semiconductor thin film 2 to be used for a thin-film transistor is deposited and patterned in order to form a gate insulating film 3. A two-layer conductive film used to constitute pixel-adding capacitance is composed of the polycrystalline silicon thin films which have been doped with the impurity; however, it may be composed of metal thin films; it is not always required that the groove 11 is filled; considering its flatness, the groove is preferably filled.