view_exposed_taxonomy_show_taxonmy_tree.php

<?php
/**
 * Implementing hook_form_alter()
 * @param $form
 * @param $form_state
 * @param $form_id
 */
function YOUR_MODULE_NAME_form_alter(&$form, $form_state, $form_id) {
    if ($form_id == 'views_exposed_form') {
        $term_reference_tree_path = drupal_get_path('module', 'term_reference_tree');
        // You should give , your exposed taxonomy field
        $form['your-toxonomy-field'] = array(
            //s'#title' => t('Tree'),
            '#type' => 'checkbox_tree',
            '#max_choices' => 999,
            '#max_depth' => 999,
            '#field_name' => 'custom_name',
            // '#leaves_only' => 1,
            '#start_minimized' => TRUE,
            '#depth' => 0,
            '#vocabulary' => taxonomy_vocabulary_load(3), // instead of '3', Your vocabulary term ID 
            '#parent_tid' => 0,
            '#value_key' => 'tid',
            '#select_parents' => TRUE,
            '#attached' => array(
                'js' => array($term_reference_tree_path . '/term_reference_tree.js'),
                'css' => array($term_reference_tree_path . '/term_reference_tree.css')
            ),
            '#attributes' => array('class' => array('field-widget-term-reference-tree')),
            '#element_validate' => array('_term_reference_tree_widget_validate'),
            '#value' => array(),
            '#filter_view' => '',
            '#token_display' => ''
        );
    }

}