Display device and piezoelectric sensor

A display device comprising:

• a display panel;
• and
• a piezoelectric sensor adjacently disposed to the display panel, the piezoelectric sensor including:
• a substrate having a first area and a second area that is different from the first area,
• a plurality of sensing transistors that are disposed on the first area of the substrate, wherein the plurality of sensing transistors are not disposed on the second area,
• a first electrode that is on the plurality of sensing transistors,
• a piezoelectric material layer that is on the first electrode, and
• a second electrode on the piezoelectric material layer,
• wherein the piezoelectric material layer has a first thickness in the first area in which the plurality of sensing transistors are disposed and has a second thickness which is greater than the first thickness in the second area in which the plurality of sensing transistors are not disposed.

A piezoelectric sensor comprising:

• a lower substrate having a first area and a second area different from the first area;
• a plurality of sensing transistors that are disposed on the first area of the lower substrate, wherein the plurality of sensing transistors are not disposed on the second area;
• a lower electrode that is disposed to cover the plurality of sensing transistors;
• a piezoelectric material layer that is disposed on the lower electrode;
• and
• an upper electrode that is disposed on the piezoelectric material layer,
• wherein a thickness of the piezoelectric material layer in the second area in which the plurality of sensing transistors are not disposed varies when the piezoelectric sensor contracts or stretches.

A piezoelectric sensor comprising:

• a substrate having a first area and a second area different from the first area;
• a plurality of sensing transistors that are disposed on the first area of the substrate, wherein the plurality of sensing transistors are not disposed on the second area;
• a first electrode that is on the plurality of sensing transistors;
• a piezoelectric material layer that is on the first electrode;
• and
• a second electrode that is disposed on the piezoelectric material layer,
• wherein at least one hole structure is formed in the first electrode or the second electrode in the second area in which the plurality of sensing transistors are not disposed.

A piezoelectric sensor comprising:

• a substrate having a first area and a second area different from the first area;
• a plurality of sensing transistors that are disposed on the first area of the substrate;
• a first electrode that is on the plurality of sensing transistors;
• a piezoelectric material layer that is on the first electrode;
• and
• a second electrode that is on the piezoelectric material layer,
• wherein, the piezoelectric sensor in operation, generates ultrasonic waves,
• wherein a wavelength of ultrasonic waves which are generated in the first area in which the sensing transistors are disposed and a wavelength of ultrasonic waves which are generated in the second area in which the sensing transistors are not disposed are different from each other.