A thin film transistor display panel a includes a transparent substrate; a gate electrode positioned on the substrate; a gate insulating layer positioned on the gate electrode; a semiconductor layer positioned on the gate insulating layer and including a channel region; a source electrode and a drain electrode positioned on the semiconductor layer and facing each other; and a passivation layer configured to cover the source electrode, the drain electrode, and the semiconductor layer, wherein the semiconductor layer includes a relatively thick first portion between the source electrode and the gate electrode and a relatively thinner second portion between the drain electrode and the gate electrode overlap, the relatively thick first portion being sufficiently thick to substantially reduce a charge trapping phenomenon that may otherwise occur at a gate electrode to gate dielectric interface if the first portion were as thin as the second portion.