Electrostatic capacitance detection device and smart card

1. An electrostatic capacitance detection device for detecting electrostatic capacitance that changes in accordance with a distance from a target object to read surface contours of the target object, comprising:

electrostatic capacitance detection elements arranged in M rows and N columns;

a power supply line supplying power to the electrostatic capacitance detection elements;

an output line outputting a signal from the electrostatic capacitance detection elements;

M row lines selecting the electrostatic capacitance detection elements disposed on a specific row; and

N column lines selecting the electrostatic capacitance detection elements disposed on a specific column, wherein:

the electrostatic capacitance detection elements each includes:

a) a signal detection element storing a charge in accordance with the electrostatic capacitance;

b) a row selection element causing the electrostatic capacitance detection element to enter a selected state in response to a signal from the row line;

c) a column selection element causing the electrostatic capacitance detection element to enter a selected state in response to a signal from the column line; and

d) a signal amplification element amplifying a signal corresponding to the charge stored in the signal detection element, wherein

the signal detection element includes a capacitance detection electrode and a reference capacitor;

the signal amplification element is a thin-film semiconductor device for signal amplification including a source electrode, a drain electrode and a gate electrode;

the row selection element is a thin-film semiconductor device for row selection including a source electrode, a drain electrode and a gate electrode;

the column selection element is a thin-film semiconductor device for column selection including a source electrode, a drain electrode and a gate electrode;

the reference capacitor includes a reference capacitor first electrode, a reference capacitor dielectric film and a reference capacitor second electrode;

the gate electrode of the thin-film semiconductor device for signal amplification, the capacitance detection electrode, and the reference capacitor second electrode are coupled to each other;

the gate electrode of the thin-film semiconductor device for row selection is coupled to the row line;

the gate electrode of the thin-film semiconductor device for column selection is coupled to the column line;

the source electrode and the drain electrode of the thin-film semiconductor device for signal amplification, the source electrode and the drain electrode of the thin-film semiconductor device for row selection, and the source electrode and the drain electrode of the thin-film semiconductor device for column selection are coupled in series between the power supply line and the output line; and

on-resistance of the thin-film semiconductor device for row selection and on-resistance of the thin-film semiconductor device for column selection are smaller than on-resistance of the thin-film semiconductor device for signal amplification.

2. The electrostatic capacitance detection device according to claim 1 , wherein:

the source electrode of the thin-film semiconductor device for signal amplification is coupled to the power supply line;

the drain electrode of the thin-film semiconductor device for signal amplification is coupled to the source electrode of the thin-film semiconductor device for column selection;

the drain electrode of the thin-film semiconductor device for column selection is coupled to the source electrode of the thin-film semiconductor device for row selection; and

the drain electrode of the thin-film semiconductor device for row selection is coupled to the output line.

3. The electrostatic capacitance detection device according to claim 1 , wherein the reference capacitor first electrode is coupled to the column line, and both the thin-film semiconductor device for signal amplification and the thin-film semiconductor device for column selection are either one of an N-type semiconductor device and a P-type semiconductor device.

4. The electrostatic capacitance detection device according to claim 1 , wherein the reference capacitor first electrode is coupled to the row line, and both the thin-film semiconductor device for signal amplification and the thin-film semiconductor device for row selection are either one of an N-type semiconductor device and a P-type semiconductor device.

5. The electrostatic capacitance detection device according to claim 1 , wherein the output line is individually provided for each column.

6. The electrostatic capacitance detection device according to claim 1 , wherein a reference capacitor capacitance C R is more than one order of magnitude larger than a transistor capacitance C T of the thin-film semiconductor device for signal amplification, if the reference capacitor capacitance C R and the transistor capacitance C T are defined as follows:

C R =ε 0 ·ε R ·S R /t R

C T =ε 0 ·ε ox ·S T /t ox

where S R (μm 2 ) is an area of an electrode of the reference capacitor, t R (μm) is a thickness of the reference capacitor dielectric film, ε R is a relative dielectric constant of the reference capacitor dielectric film, S T (μm 2 ) is an area of the gate electrode of the thin-film semiconductor device for signal amplification, t ox (μm) is a thickness of a gate insulating film of the thin-film semiconductor device for signal amplification, ε ox is a relative dielectric constant of the gate insulating film, and ε 0 is a permittivity in vacuum.

7. A smart card comprising:

a target object detection sensor that detects surface contours of a target object, the target object detection sensor being made up of the electrostatic capacitance detection device according to claim 1 ; and

an integrated circuit.