Keyboard device and key structure thereof

A keyboard device comprising plural key structures, wherein each key structure comprises:

• a plate assembly having a hollow region;
• a keycap located over the plate assembly, and comprising at least one hook;
• two connecting members connected between the keycap and the plate assembly, and each of the two connecting members having an upper end connected to the keycap and a lower end connected to the plate assembly, wherein the keycap is connected with the upper end of one of the connecting members through the at least one hook, and the keycap is movable upwardly or downwardly relative to the plate assembly through the two connecting members;
• and
• a buffering element installed on the plate assembly, wherein the buffering element is extended in a direction toward the keycap and penetrated through the hollow region of the plate assembly, wherein a top surface of the buffering element is lower than a top surface of the plate assembly, and a vertical projection of the top surface of the buffering element is separated from vertical projections of the lower ends of the two connecting members,
• wherein while the keycap is moved downwardly toward the plate assembly and the at least one hook of the keycap is contacted with the top surface of the buffering element, there is the gap between the keycap and the plate assembly.