A device having thin-film transistor (TFT) floating gate memory cell structures is provided. The device includes a substrate, a dielectric layer on the substrate, and one or more source or drain regions being embedded in the dielectric layer. the dielectric layer being associated with a first surface. Each of the one or more source or drain regions includes an N+ polysilicon layer on a diffusion barrier layer which is on a first conductive layer. The N+ polysilicon layer has a second surface substantially co-planar with the first surface. Additionally, the device includes a P− polysilicon layer overlying the co-planar surface and a floating gate on the P− polysilicon layer. The floating gate is a low-pressure CVD-deposited silicon layer sandwiched by a bottom oxide tunnel layer and an upper oxide block layer. Moreover, the device includes at least one control gate made of a P+ polysilicon layer overlying the upper oxide block layer. A method of making the same memory cell structure is provided and can be repeated to integrate the structure three-dimensionally.