Short Channel Effect: It is the decrease of Vt with the reduction of channel length L
DIBL, Drain Induced Barrier Lowering: As Vds increases, the drain-body depletion region increases and as a result the channel length decreases thus reducing Vt.
Channel Length Modulation: As Vds increases beyond Vd-sat, the saturation point where the surface channel collapses begins to move slightly towards the source, thereby decreasing the effective channel length and decreasing Vt
Note: More device issues in the future