That's the way iOS 7 system buttons look like.
If you want to simulate the iOS 6 look, change it to a custom button, set your own background, and do something like:
First add #import <QuartzCore/QuartzCore.h>
framework to your .m file and use following code for your button.
button.layer.cornerRadius = 4;
button.clipToBounds = YES;
button.layer.borderColor = [UIColor {your color here}].CGColor;
button.layer.borderWidth = 1;