5v voltage regulator problem

i have designed 5v voltage regulator using LM2940 ,with .1uf capacitor at input and 100 uf at output of LM2940. when i connected contineous roation servo motor to o/p of this regulator circuit means 5v to red wire of servo motor ,ground to black wire of servo motor.
White wire of rc servo is for signal . but without connecting this signal wire of this servo to any other point(open) and making supply ON (5*AA batteries) ,servo motor is rotating. and after disconnecting i/p supply ,pin no1 of LM2940 showing .7V ,What should be problem in this circuit

No problem. Having a servo with power applied but without a valid control signal is just not a defined mode for a servo to operate in. They are not designed to to run that way.