Abstract: A thin film transistor is produced by applying onto a non-silicon foundation, a thin film of silicon semiconductor material under such conditions that polycrystalline or microcrystalline material is formed. Source and/or drain regions of doped semiconductor material are then formed onto the film; following by applying insulating material onto the film, and a gate region onto the insulating material. The source and/or drain regions are applied so that such regions have a crystalline structure that depends upon the crystalline structure of the underlying thin film. The resulting source and drain regions have high lateral conductivity so that source and drain contacts can be made with reduced cross-sectional areas. The method may employ a self-alignment process to simplify device production.