Tuning fork crystal oscillation plate and method of manufacturing the same

1. A tuning fork crystal oscillation plate comprising:

a tuning fork crystal oscillation piece including a base with a substantially rectangular shape when seen from the top, and at least two oscillation arms extending in the same direction from one side of said base and having substantially rectangular shapes when seen from the top, said at least two oscillation arms including first and second oscillation arms;

first and second grooves which are formed in one main surface of said first oscillation arm and one main surface of said second oscillation arm on the same side, said first groove and said second groove extending from a boundary line of said base with said first and second oscillation arms toward distal ends of said first oscillation arm and said second oscillation arm, said first groove and said second groove having a length that falls within a range of 50% (inclusive) to 70% (exclusive) a length of said first oscillation arm and said second oscillation arm, and said first groove and said second groove having a depth that falls within a range of 50% to 90% (both inclusive) a thickness of said tuning fork crystal oscillation piece;

first and second groove electrodes which are formed on inner surfaces of said first and second grooves, respectively

first side surface electrodes which are formed on two side surfaces, respectively, of said first oscillation arm; and

second side surface electrodes which are formed on two side surfaces, respectively, of said second oscillation arm,

wherein said first groove electrode is connected to said second side surface electrodes to constitute one terminal, and

said second groove electrode is connected to said first side surface electrodes to constitute the other terminal.

2. A plate according to claim 1 , further comprising:

a first flat electrode formed on the other main surface of said first oscillation arm to oppose said first groove electrode, and connected to said second side surface electrodes together with said first groove electrode; and

a second flat electrode formed on the other main surface of said second oscillation arm to oppose said second groove electrode, and connected to said first side surface electrodes together with said second groove electrode.

3. A plate according to claim 1 , further comprising:

a first distal end electrode formed on a surface of a distal end of the other main surface of said first oscillation arm and connected to said second groove electrode together with said first side surface electrodes; and

a second distal end electrode formed on a surface of a distal end of the other main surface of said second oscillation arm and connected to said first second groove electrode together with said second side surface electrodes,

wherein said first distal end electrode and said second distal end electrode adjust a resonant frequency of said tuning fork crystal oscillation plate.

4. A plate according to claim 1 , wherein each of said first groove and said second groove comprises at least two grooves which are formed parallel to each other.

5. A plate according to claim 1 , wherein each of said first groove and said second groove has one of a substantially trapezoidal section and a substantially V-shaped section in a direction perpendicular to a longitudinal direction thereof.

6. A plate according to claim 1 , wherein said first oscillation arm and said second oscillation arm flex upon application of an alternating voltage to said two terminals.

7. A plate according to claim 6 , wherein said tuning fork crystal oscillation plate has a resonant frequency of 32 kHz to 200 kHz.