function MYTHEME_preprocess_field(&$variables, $hook) {
  // 1. field--field-name--view-mode.tpl.php
  // 2. field--field-name--content-type--view-mode.tpl.php
  $element = $variables['element'];

  $variables['theme_hook_suggestions'][] = 'field__' . $element['#field_name'] . '__' . $element['#view_mode'];
  $variables['theme_hook_suggestions'][] = 'field__' . $element['#field_name'] . '__' . $element['#bundle'] . '__' . $element['#view_mode'];
}